Refactor and expand the CI workflows

- For each OS, builds of the default compiler plus the
  latest-supported compilers are run. When multiple operating systems
  are supported (such as Ubuntu 16.04 and latest), a build on
  the oldest OS using its default compiler is also performed.

- Debug builds are used because they often are more thorough at
  detecting coding issues (debug warning counts are higher).

- Runtime dynamic sanitizers are added and serialized per-compiler.
  Their build and runtime log-files are xz-compressed, and then
  GitHub's asset upload Zips the log directory.

- Each workflow now holds the maximum allowed compiler warnings
  per-build, so we can have tighter control of when new warnings
  are introduced (that would otherwise pass if still below the
  maximum)

- Use of github's new 'cache' feature has been leveraged to restore
  the brew, macports, and msys2 environments to eliminate the
  lenghthy setup times for those environments.  If a new cache
  is needed, then we simply increment the cache `key:` value and
  the next CI run will archive new caches. (Note that GitHub has a
  400MB limit on cache size however they have already said they
  are raising it - so we might be able to cache out longest running
  job which is MSYS+Clang)

- Where it makes sense, multi-line workflow statements have been
  broken out into .github/scripts as files to make the workflow YAML
  leaner and more readable, while giving us a richer environment in
  the scripts.

.github/scripts/build-and-run-sanitizers.sh

@@ -0,0 +1,58 @@
+#!/bin/bash
+
+# Copyright (c) 2019 Kevin R Croft <krcroft@gmail.com>
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# This simple script is used to build, test, and archive the log output from
+# various sanitizer-builds.
+#
+# Usage:
+#   ./build-and-run-sanitizers.sh COMPILER VERSION SANITIZER [SANITIZER [...]]"
+#
+# Examples:
+#   ./build-and-run-sanitizers.sh clang 8 msan usan
+#   ./build-and-run-sanitizers.sh gcc 9 asan uasan usan tsan
+#
+set -euo pipefail
+
+# Check the arguments
+if [[ "$#" -lt 3 ]]; then
+	echo "Usage: $0 COMPILER VERSION SANITIZER [SANITIZER [...]]"
+	exit 1
+fi
+
+# Defaults and arguments
+compiler="${1}"
+compiler_version="${2}"
+logs="${compiler}-logs"
+shift 2
+sanitizers=("$@")
+
+# Move to the top of our source directory
+cd "$(dirname "${0}")/../.."
+
+# Make a directory to hold our build and run output
+mkdir -p "${logs}"
+
+for sanitizer in "${sanitizers[@]}"; do
+
+	# Build DOSBox for each sanitizer
+	time ./scripts/build.sh \
+		--compiler "${compiler}" \
+		--version-postfix "${compiler_version}" \
+		--build-type "${sanitizer}" \
+		&> "${logs}/${compiler}-${sanitizer}-compile.log"
+
+	# Exercise the testcase(s) for each sanitizer
+	# Sanitizers return non-zero if one or more issues were found,
+	# so we or-to-true to ensure our script doesn't end here.
+	time xvfb-run ./src/dosbox -c exit \
+		&> "${logs}/${compiler}-${sanitizer}-EnterExit.log" || true
+
+done
+
+# Compress the logs
+(
+	cd "${logs}"
+	xz -T0 -e ./*.log
+)

.github/scripts/download-and-build-macports.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+
+# Copyright (c) 2019 Kevin R Croft <krcroft@gmail.com>
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# This script downloads and builds MacPorts from source.
+# Usage: ./download-and-build-macports.sh
+#
+set -xeuo pipefail
+
+# Move to the top of our source directory
+cd "$(dirname "${0}")/../.."
+
+# Download and install MacPorts
+git clone --quiet --depth=1 https://github.com/macports/macports-base.git
+(
+	cd macports-base
+	./configure
+	make -j"$(sysctl -n hw.physicalcpu || echo 4)"
+)

.github/scripts/install-and-update-macports.sh

@@ -0,0 +1,27 @@
+#!/bin/bash
+
+# Copyright (c) 2019 Kevin R Croft <krcroft@gmail.com>
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# This script installs and updates MacPorts from an already-compiled
+# source tree assumed to be located n a directory called
+# 'macports-base' off the root of our source-tree.
+#
+# Usage: ./install-and-update-macports.sh
+#
+set -xeuo pipefail
+
+# Ensure we have sudo rights to install MacPorts
+if [[ $(id -u) -ne 0 ]] ; then echo "Please run as root" ; exit 1 ; fi
+
+# Move to the top of our source directory
+cd "$(dirname "${0}")/../.."
+(
+	cd macports-base
+	make install
+)
+# Purge the now-unecessary source
+rm -rf macports-base
+
+# Update our ports collection
+/opt/local/bin/port -q selfupdate || true

.github/scripts/prepare-for-macports-cachehit.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+
+# Copyright (c) 2019 Kevin R Croft <krcroft@gmail.com>
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# This script creates a new writable /opt/local directory with
+# sane ownership, permissions, and attributes on the directory.
+# Usage: ./prepare-for-macports-cachehit.sh
+#
+set -xeuo pipefail
+
+# Ensure we have sudo rights to create the directory
+if [[ $(id -u) -ne 0 ]] ; then echo "Please run as root" ; exit 1 ; fi
+user="${SUDO_USER}"
+group="$(id -g "${user}")"
+
+mkdir -p /opt/local
+cd /opt/local
+chflags nouchg .
+xattr -rc .
+chmod 770 .
+chown "${user}:${group}" .

.github/scripts/reset-brew.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+
+# Copyright (c) 2019 Kevin R Croft <krcroft@gmail.com>
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# This script removes all existing brew packages, and then
+# re-installs some important basic packages (listed below).
+#
+# Usage: ./reset-brew.sh
+#
+set -xuo pipefail
+set +e
+
+# Pre-cleanup size
+sudo du -sch /usr/local 2> /dev/null
+
+# Uninstall all packages
+# shellcheck disable=SC2046
+brew remove --force $(brew list) --ignore-dependencies
+# shellcheck disable=SC2046
+brew cask remove --force $(brew cask list)
+
+# Reinstall important packages
+brew install git git-lfs python curl wget jq binutils zstd gnu-tar
+
+# Clean the brew cache
+rm -rf "$(brew --cache)"
+
+# Post-clean up size
+sudo du -sch /usr/local 2> /dev/null
+
+# This script is best-effort, so always return success
+exit 0
+

.github/scripts/shrink-brew.sh

@@ -0,0 +1,52 @@
+#!/bin/bash
+
+# Copyright (c) 2019 Kevin R Croft <krcroft@gmail.com>
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# This script reduces the size of a brew-managed installation on macOS.
+# Its main use is to shrink this area to fit within GitHub's cache
+# limits however it can also be used by end-users wanting to save space.
+#
+# Note that this script remove alot of content deemed unecessary for our
+# purposes such as ruby, go, grade, azure, etc..) so using on your
+# home system is probably not what you want :-)
+#
+# Usage: ./shrink-brew.sh
+#
+set -xuo pipefail
+set +e
+
+# Ensure we have sudo rights
+if [[ $(id -u) -ne 0 ]] ; then echo "Please run as root" ; exit 1 ; fi
+user="${SUDO_USER}"
+group="$(id -g "${user}")"
+
+# If we don't have /usr/local then brew hasn't installed anything yet
+cd /usr/local || exit 0
+
+# Purge unecessary bloat
+for dir in lib/ruby Cellar/go Cellar/gradle Cellar/azure-cli lib/node_modules \
+share/powershell Caskroom/fastlane Cellar/ruby opt/AGPM Caskroom Cellar/node \
+miniconda Cellar/python@2 Cellar/git lib/python2.7 Cellar/git-lfs Cellar/subversion \
+Cellar/maven Cellar/aria2 Homebrew/Library/Homebrew/os/mac/pkgconfig/fuse \
+.com.apple.installer.keep microsoft; do
+	rm -rf "${dir}" || true
+done
+
+# Cleanup permissions and attributes
+chflags nouchg .
+find . -type d -exec xattr -c {} +
+find . -type f -exec xattr -c {} +
+chown -R "${user}:${group}" ./*
+find . ! -path . -type d -exec chmod 770 {} +
+
+# Binary-stripping is *extremely* verbose, so we send these to the ether
+find Cellar -name '*' -a ! -iname 'strip' -type f -perm +111 -exec strip {} + &> /dev/null
+find Cellar -name '*.a' -type f -exec strip {} + &> /dev/null
+
+# Post-cleanup size check
+du -sch . 2> /dev/null
+
+# This entire script is best-effort, so always return success
+exit 0
+

.github/scripts/shrink-macports.sh

@@ -0,0 +1,36 @@
+#!/bin/bash
+
+# Copyright (c) 2019 Kevin R Croft <krcroft@gmail.com>
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# This script reduces the size of a MacPorts installation
+# under macOS. Its main use is to shrink this area to fit within
+# GitHub's cache limits; however it can also be used by end-users
+# wanting to save space.
+#
+# Usage: ./shrink-macports.sh
+#
+set -xuo pipefail
+set +e
+
+# If MacPorts doesn't exist then our job here is done!
+cd /opt/local || exit 0
+
+# Ensure we have sudo rights
+if [[ $(id -u) -ne 0 ]] ; then echo "Please run as root" ; exit 1 ; fi
+
+# Cleanup permissions and attributes
+chflags nouchg .
+find . -type d -exec xattr -c {} +
+find . -type f -exec xattr -c {} +
+
+for dir in var/macports libexec/macports share/man; do
+	rm -rf "${dir}" &> /dev/null || true
+done
+
+# Binary-stripping is extremely verbose, so send these to the ether
+find . -name '*' -a ! -iname 'strip' -type f -perm +111 -exec ./bin/strip {} + &> /dev/null
+find . -name '*.a' -type f -exec ./bin/strip {} + &> /dev/null
+
+# This entire script is best-effort, so always return success
+exit 0

.github/scripts/shrink-msys2.sh

@@ -0,0 +1,44 @@
+#!/bin/bash
+
+# Copyright (c) 2019 Kevin R Croft <krcroft@gmail.com>
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# This script reduces the size of an MSYS2 and MingGW installation
+# under Windows. Its main use is to shrink these areas to fit within
+# GitHub's cache limits; however it can also be used by end-users wanting
+# to save space.
+#
+# Usage: ./shrink-msys2.sh
+#
+set -xuo pipefail
+set +e
+
+# Clean all the package archives from pacman
+pacman -Scc --noconfirm
+
+# Strip binaries using their associated striping tool
+for dir in /usr /mingw32 /mingw64; do
+
+	# Enter our directory if we have it
+	cd "${dir}" || continue
+
+	# Check if we have an associated stripping tool
+	if [[ ! -f "bin/strip.exe" ]]; then continue; fi
+
+	# Start stripping
+	find . -type f              \
+		\( -iname '*.exe'       \
+		   -or -iname '*.a'     \
+		   -or -iname '*.dll'   \
+		   -or -iname '*.so'    \
+		\)                      \
+		-a ! -iname 'strip.exe' \
+		-print0                 \
+	| xargs -0 ./bin/strip.exe --strip-unneeded
+done
+
+# Delete MinGW's share directories
+rm -rf /mingw*/share
+
+# This entire script is best-effort, so always return success
+exit 0

.github/scripts/tar

@@ -0,0 +1,19 @@
+#!/bin/bash
+set -euo pipefail
+rcode=0
+# If we're running outside of GitHub then run tar normally
+if [[ -z "${GITHUB_WORKFLOW:-}" ]]; then
+	"/usr/local/bin/gtar" "$@"
+	rcode="$?"
+# Otherwise use zstd and ignore tar's return-code
+else
+	first_arg="${1/z/}"
+	shift
+	[[ "${first_arg}" == "-x" ]] && decomp="-d" || decomp=""
+	set +e -x
+	"/usr/local/bin/gtar" \
+		--warning=none \
+		--use-compress-program="zstd -T0 -19 --long=31 --no-progress -v ${decomp}" \
+		"${first_arg}" "$@"
+fi
+exit "${rcode}"