fix macOS CI (#496)

### Description
The macOS GitHub runner is broken once again due to broken Homebrew
packages.

We fix this by installing a specific version of Python using
`actions/setup-python` instead of `brew install python3` and by
specifying `brew install [email protected]` (since the Homebrew `[email protected]`
package is broken due to
Homebrew/homebrew-core#159165).

### Checklist
_Before this pull request can be reviewed, all of these tasks should be
completed. Denote completed tasks with an `x` inside the square brackets
`[ ]` in the Markdown source below:_
- [x] I have added a description (see above).
- [ ] I have added a link to any related issues see (see above).
- [x] I have read the [Contributing
Guide](https://github.com/quokka-astro/quokka/blob/development/CONTRIBUTING.md).
- [ ] I have added tests for any new physics that this PR adds to the
code.
- [ ] I have tested this PR on my local computer and all tests pass.
- [ ] I have manually triggered the GPU tests with the magic comment
`/azp run`.
- [ ] I have requested a reviewer for this PR.

.github/workflows/cmake-macos.yml

@@ -24,6 +24,11 @@ jobs:
       with:
         submodules: true
         fetch-depth: 0  # Shallow clones should be disabled for a better relevancy of sonarcloud analysis
+
+    - uses: actions/setup-python@v5
+      with:
+        python-version: '3.11'
+        cache: 'pip' # caching pip dependencies
 
     - name: Create Build Environment
       # Some projects don't allow in-source building, so create a separate build directory
@@ -32,8 +37,14 @@ jobs:
 
     - name: Install Homebrew dependencies
       run: |
-        brew install python3 openmpi hdf5 || true
-        brew link --overwrite [email protected]
+        brew install openmpi [email protected] || true
+        brew link --force [email protected]
+
+    - name: Output HDF5 configuration (verbose)
+      run: h5cc -showconfig
+
+    - name: Output HDF5 compile flags
+      run: h5cc -show
 
     - name: Install pip dependencies
       run: python3 -m pip install --user numpy matplotlib