Used setup-msys from the msys org

This, since it was sanctioned, may work better. Let's see how it's gonna build...

.github/workflows/cmake-multi-platform.yml

@@ -50,15 +50,24 @@ jobs:
     steps:
     - uses: actions/checkout@v4
 
-    - name: Install MSYS Packages
-      run: C:/msys64/msys -c "pacman -Syuu mingw-w64-ucrt-x86_64-toolchain pacman -S mingw-w64-ucrt-x86_64-ffcall pacman -S mingw-w64-ucrt-x86_64-cmake --noconfirm"
+    - name: Setup MSYS, add to path
+      uses: msys2/setup-msys2@v2
+      with:
+        msystem: ucrt64
+        update: true
+        install: >-
+          mingw-w64-ucrt-x86_64-toolchain
+          mingw-w64-ucrt-x86_64-ffcall 
+          mingw-w64-ucrt-x86_64-cmake
       
     - name: Configure CMake
       # Configure CMake in a 'build' subdirectory. `CMAKE_BUILD_TYPE` is only required if you are using a single-configuration generator such as make.
       # See https://cmake.org/cmake/help/latest/variable/CMAKE_BUILD_TYPE.html?highlight=cmake_build_type
+      shell: msys2
       run: cmake -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -G "MinGW Makefiles"
 
     - name: Build
+      shell: msys2
       # Build your program with the given configuration
       run: cmake --build ${{github.workspace}}/build --config ${{env.BUILD_TYPE}}