Unify Windows installations

The commit switches from installing gcc or clang under Windows to
simply always installing clang (which also installs gcc as a dependency).
This ensures that cache's produced from a gcc-specific builds will
be compatible with clang builds.

.github/workflows/config.yml

@@ -60,7 +60,7 @@ jobs:
           steps.repo-meta.outputs.has-commits == 'true'
         with:
           path: 'C:/tools/msys64'
-          key: msys2-GCC-64-${{ steps.get-date.outputs.date }}-2
+          key: msys2-64-${{ steps.get-date.outputs.date }}-2
 
       - name:  Install MSYS2 (Windows)
         if:    >
@@ -76,7 +76,7 @@ jobs:
           steps.repo-meta.outputs.has-commits == 'true'
         shell: python scripts\msys-bash.py {0}
         run:   |
-           scripts/list-build-dependencies.sh -m msys2 -c gcc ${{ matrix.conf.without_packages }} | xargs pacman -S --noconfirm
+           scripts/list-build-dependencies.sh -m msys2 -c clang ${{ matrix.conf.without_packages }} | xargs pacman -S --noconfirm
            .github/scripts/shrink-msys2.sh
 
       - name:  Install dependencies ${{ matrix.conf.without_packages }} (Linux)

.github/workflows/windows.yml

@@ -50,7 +50,7 @@ jobs:
       - name:  Install C++ compiler and libraries
         if:    steps.cache-msys2.outputs.cache-hit != 'true'
         shell: python scripts\msys-bash.py {0}
-        run:   ./scripts/list-build-dependencies.sh -m msys2 -c ${{ matrix.conf.compiler }} -b ${{ matrix.conf.bits }} | xargs pacman -S --noconfirm
+        run:   ./scripts/list-build-dependencies.sh -m msys2 -c clang -b ${{ matrix.conf.bits }} | xargs pacman -S --noconfirm
       - name:  Shrink MSYS2 for cache
         if:    steps.cache-msys2.outputs.cache-hit != 'true'
         shell: python scripts\msys-bash.py {0}