Simplify package listing script and standardize workflows

The commit makes the following changes:
 - The package listing script now requires the user specify which package manager
   they're using. This approach resolves the ambiguity if a system has more than
   one package manager (ie: macports & brew)

 - Adds packages for Fedora, RedHat/CentOS, Arch, and OpenSuse

 - Eliminates unecessary code in the package manager script
   (more can be eliminate at the expense of complexity)

 - Made a couple minor fixes to the build script

 - Tried to further "standardize" the workflows as follows:

     - names are Compiler Version (Environment)

     - Sorted them alphabetically in their respective YAMLs

     - Minor spacing adjustment to align values (where it makes sense)

     - Dropped quotes around some of the string values because I'd
       rather our YAML be consistent and propper instead of changing our
       YAML to suite the limitations of an editor (can a different plugin
       or better parser be used?)

     - Added macOS workflows for Homebrew and MacPorts, both ready to
       go and tested, but with the build step just commented out

scripts/build.md

@@ -1,33 +1,30 @@
-# DOSBox build script
+# DOSBox Build Script
 
-A helper-script that builds DOSBox with varying compilers, release types, and versions
-on MacOS, Linux, and Windows.
+A script that builds DOSBox with your choice of compiler, release types, and
+additional optimization options on MacOS, Linux, and Windows.
 
-A second script, **list-build-dependencies.sh** prints a list of package and library
-dependencies used to build and link DOSBox, customized for your hardware, operating system,
-and selected compiler and its version.  You can use this script's output to install
-those necessary packages.
+If this is the first time you are attempting to build DOSBox, then you need to
+first install the development tools and DOSBox's development packages prior to
+building. To help in this regard, the **list-build-dependencies.sh** script
+prints a list of packages that you can use to install these dependencies.
+
+Use of both scripts is described below.
 
 ## Requirements
 
 - **Windows newer than XP**
     - **NTFS-based C:**, because msys2 doesn't work on FAT filesystems
-	- **Chocolately**, to install msys2
-
 - **MacOS** 10.x
-	- **brew**, as the package manager
-
 - **Ubuntu** 16.04 or newer
-	- **apt**, as the package manager
-	- **sudo**, to permit installation of depedencies (optional) 
-
-- **Build dependencies (all operating systems)**
-    - Per those listed by the accompanying list-build-dependencies.sh script
+- **Fedora** up-to-date
+- **RedHat or CentOS** 7 or newer
+- **Arch-based distribution** up-to-date
+- **OpenSUSE Leap** 15 or newer
 
 ## Windows Installation and Usage
 
 1. Download and install Chocolatey: https://chocolatey.org/install
-1. Open a console and run Cholocatey's command line interface (CLI) to install msys2:  
+1. Open a console and run Cholocatey's command line interface (CLI) to install msys2 and git:  
    `choco install msys2 git --no-progress`
 
     ```
@@ -47,48 +44,82 @@ those necessary packages.
    PATH environment variable does not have C:\tools\msys64 in it. Adding...
    ```
 
-1. Open a new console and clone the DOSBox staging repository:  
-   `git clone https://github.com/dreamer/dosbox-staging.git`
+1. Launch a new MSYS2 terminal (not a CMD prompt or Powershell window):
+    1. Start Menu > Run ... `c:\tools\msys64\msys2_shell.cmd`
+    1. Run all subsequent steps within this terminal.
 
-1. [optional] Install the build tools and package dependencies, if not yet done so:
-   ``` shell
-   cd dosbox-staging
-   SET CWD=%cd%
-   bash -lc "pacman -S --noconfirm $($CWD/scripts/list-build-dependencies.sh)"
-   ```
+1. Clone and enter the repository's directory:
+    1. `git clone https://github.com/dreamer/dosbox-staging.git`
+    1. `cd dosbox-staging`
+    1. Run all subsequent steps while residing in the repo's directory.
+
+1. (🏁 first-time-only) Install the build tools and package dependencies:  
+   `./scripts/list-build-dependencies.sh -p msys2 | xargs pacman -S --noconfirm`
+
+1. Launch the build script with default settings:  
+   `./scripts/build.sh --bin-path /mingw64/bin`
 
-1. Launch the build script with default settings:
-   ``` shell
-   cd dosbox-staging
-   SET CWD=%cd%
-   bash -lc "$CWD/scripts/build.sh --bin-path /mingw64/bin --src-path $CWD"
-   ```
 
 ## MacOS Installation and Usage
 
-1. Download and install brew: https://brew.sh
-1. Install git: `brew install git`
+Builds on Mac can be performed with Clang or GCC.
+
+If you only plan on only building with Clang, then follow the Brew installation steps.
+If you're interested in building with GCC, then either Brew or MacPorts will work.
+Both can be installed without conflicting with eachother.
+
+Before installing either, the Xcode tools need to be installed and the license agreed to:
+
+###  Xcode Installation
+1. Install the command line tools: `xcode-select --install`
+1. Accept the license agreement: `sudo xcodebuild -license`
+
+
+### Brew Installation
+1. Download and install brew per the instructions here: https://brew.sh
+1. Update it with: `brew update`
+1. Install git with: `brew install git`
+1. Install DOSBox dependencies: `brew install $(./scripts/list-build-dependencies.sh -p brew)`
+
+
+### MacPorts Installation
+
+1. Build and install MacPorts along with DOSBox dependencies with the following sequence:
+
+    ``` shell
+    git clone --quiet --depth=1 https://github.com/macports/macports-base.git
+    cd macports-base
+    ./configure
+    make -j"$(sysctl -n hw.physicalcpu || echo 4)"
+    sudo make install
+    PREFIX="/opt/local"
+    PATH="${PREFIX}/sbin:${PREFIX}/bin:${PATH}"
+    sudo port -q selfupdate
+    sudo port -q install $(/scripts/list-build-dependencies.sh -p macports)
+    ```
+
+### Build DOSBox (common for all of the above)
+
 1. Clone the repository: `git clone https://github.com/dreamer/dosbox-staging.git`
 1. Change directories into the repo: `cd dosbox-staging`
-1. [optional] Install the build tools and package dependencies, if not yet done so:
-   ``` shell
-   brew update
-   brew install $(./scripts/list-build-dependencies.sh)
-   ```
-1. Build DOSBox: `./scripts/build.sh`
+1. Build DOSBox:
+    - Clang: `./scripts/build.sh --compiler clang --bin-path /usr/local/bin`
+    - GCC (brew): `./scripts/build.sh --compiler-version 9 --bin-path /usr/local/bin`
+    - GCC (macports): `./scripts/build.sh --compiler-version mp-9 --bin-path /opt/local/bin`
 
-## Linux (Ubuntu/Debian-based) Installation and Usage
+## Linux Installation
+
+1. (🏁 first-time-only) Install dependencies based on your package manager; apt in this example:  
+    `sudo apt install -y $(./scripts/list-build-dependencies.sh -p apt)`  
+    For other supported package managers, run:  
+    `./scripts/list-build-dependencies.sh --help`
 
 1. Install git: `sudo apt install -y git`
 1. Clone the repository: `git clone https://github.com/dreamer/dosbox-staging.git`
 1. Change directories into the repo: `cd dosbox-staging`
-1. [optional] Install the build tools and package dependencies, if not yet done so:
-   ``` shell
-   sudo apt update -y
-   sudo apt install -y $(./scripts/list-build-dependencies.sh)
-   ```
 1. Build DOSBox: `./scripts/build.sh`
 
+
 ## Additional Tips
 
 The compiler, version, and bit-depth can be selected by passing the following common
@@ -97,7 +128,7 @@ options to the **list-build-dependencies.sh** and **build.sh** scripts:
 * `--compiler-version 8`, to use a specific version of compiler (if available in your package manager)
 * `--bit-depth 32`, to build a 32-bit binary instead of 64-bit
 
-After building, your binary will reside inside the src/ directory.
+After building, your `dosbox` or `dosbox.exe` binary will reside inside `./dosbox-staging/src/`.
 
 Build flags you might be interested in:
 * `--release debug`, to build a binary containing debug symbols (instead of **fast** or **small**)
@@ -107,4 +138,3 @@ The above flags are othogonal and thus can be mixed-and-matched as desired.
 
 If you want to run multiple back-to-back builds from the same directory with different settings then
 add the `--clean` flag to ensure previous objects and binaries are removed.
-