Set the upper limit on warnings number

This way it will be possible to prevent users from introducing new
warnings. As new fixes will be upstreamed, the maximum limit of
allowed warnings should be taken lower and lower, so this script
could be eventually replaced by -Werror.

.github/workflows/compilation.yml

@@ -20,8 +20,10 @@ jobs:
           set -x
           $CXX --version
           ./autogen.sh
-          ./configure
-          make -j "$(nproc)"
+          ./configure CXXFLAGS="-Wall -fdiagnostics-color=always"
+          make -j "$(nproc)" |& tee build.log
+      - name: Summarize warnings
+        run: python3 ./scripts/count-warnings.py build.log
 
   build_gcc8:
     name: "GCC 8 (ubuntu-18.04)"
@@ -39,8 +41,10 @@ jobs:
           set -x
           $CXX --version
           ./autogen.sh
-          ./configure
-          make -j "$(nproc)"
+          ./configure CXXFLAGS="-Wall -fdiagnostics-color=always"
+          make -j "$(nproc)" |& tee build.log
+      - name: Summarize warnings
+        run: python3 ./scripts/count-warnings.py build.log
 
   build_ubuntu:
     name: "GCC"
@@ -58,8 +62,10 @@ jobs:
           set -x
           g++ --version
           ./autogen.sh
-          ./configure
-          make -j "$(nproc)"
+          ./configure CXXFLAGS="-Wall -fdiagnostics-color=always"
+          make -j "$(nproc)" |& tee build.log
+      - name: Summarize warnings
+        run: python3 ./scripts/count-warnings.py build.log
 
   build_clang:
     name: "Clang 6 (ubuntu-18.04)"
@@ -77,8 +83,10 @@ jobs:
           set -x
           $CXX --version
           ./autogen.sh
-          ./configure
-          make -j "$(nproc)"
+          ./configure CXXFLAGS="-Wall"
+          make -j "$(nproc)" |& tee build.log
+      - name: Summarize warnings
+        run: python3 ./scripts/count-warnings.py build.log
 
   build_macos:
     name: "Clang (macOS-10.14)"
@@ -93,5 +101,7 @@ jobs:
           set -x
           clang++ --version
           ./autogen.sh
-          ./configure
-          make -j "$(sysctl -n hw.physicalcpu)"
+          ./configure CXXFLAGS="-Wall"
+          make -j "$(sysctl -n hw.physicalcpu)" 2>&1 | tee build.log
+      - name: Summarize warnings
+        run: python3 ./scripts/count-warnings.py build.log