Add missing packages for msys2 as per https://www.msys2.org/docs/ci/

.github/workflows/ccpp.yml

@@ -40,6 +40,10 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - uses: msys2/setup-msys2@v1
+      with:
+          msystem: MINGW64
+          update: true
+          install: git mingw-w64-x86_64-toolchain
     - name: make check
       run: make CC="gcc -std=c99 -D__USE_MINGW_ANSI_STDIO=1" check