ci: use the default C compiler on Apple

Author: aminya

.github/workflows/CI.yml

@@ -46,12 +46,20 @@ jobs:
 
       # Setup compilers and tools
       - name: Setup Cpp
+        if: ${{ !contains(matrix.os, 'macos') }}
         uses: aminya/setup-cpp@v1
         with:
           compiler: ${{ matrix.compiler }}
           cmake: true
           ninja: true
 
+      - name: Setup Cpp
+        if: ${{ contains(matrix.os, 'macos') }}
+        uses: aminya/setup-cpp@v1
+        with:
+          cmake: true
+          ninja: true
+
       - name: Setup D
         uses: dlang-community/setup-dlang@v1
         with: