Update runner for MinGW static CI and install cmake in msys2 shell.

Author: cboulay

.github/workflows/mingw_static.yml

@@ -19,7 +19,7 @@ jobs:
   build:
     name: MinGW batteries-included
     runs-on: windows-latest
-    
+
     defaults:
       run:
         shell: 'msys2 {0}'
@@ -29,6 +29,9 @@ jobs:
     - uses: msys2/setup-msys2@v2
       with:
         release: false
+        cache: true
+        install: >-
+            cmake
     - name: Configure CMake
       run: |
            cmake --version
@@ -41,7 +44,7 @@ jobs:
                 -Dlslgitrevision=${{ github.sha }} \
                 -Dlslgitbranch=${{ github.ref }} \
                 -DLSL_OPTIMIZATIONS=OFF \
-                -G 'MSYS Makefiles'
+                -G Ninja
 
     - name: make
       run: cmake --build build --target install --config Release -j --verbose