cibuild.yml: correctly check for macOS when determining the need of m…

…acOS packages installation

https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/evaluate-expressions-in-workflows-and-actions

.github/workflows/cibuild.yml

@@ -127,7 +127,7 @@ jobs:
  libvorbis-dev:${{ matrix.platform.arch }}
 
  - name: Install macOS packages
- if: ${{ matrix.platform.name == 'macOS' }}
+ if: ${{ startsWith(matrix.platform.name, 'macOS') }}
  run: |
  brew update
  brew install sdl2 lzo libogg libvorbis theora