fix: ci macos (#10020)

Signed-off-by: fufesou <linlong1266@gmail.com>

.github/workflows/flutter-build.yml

@@ -690,7 +690,13 @@ jobs:
 
       - name: Install build runtime
         run: |
-          brew install llvm create-dmg nasm cmake gcc wget ninja pkg-config
+          brew install llvm create-dmg nasm cmake gcc wget ninja
+          # pkg-config is handled in a separate step, because it may be already installed by `macos-latest`(14.7.1) runner
+          if command -v pkg-config &>/dev/null; then
+              echo "pkg-config is already installed"
+          else
+              brew install pkg-config
+          fi
 
       - name: Install flutter
         uses: subosito/flutter-action@v2