ci: fix tests on macOS 14 + Python 3.9

Avoid compiling pyobjc-core and requiring a compiler for this specific
combination. We now use the precompiled pyobjc wheel (<=11.0) to avoid
the issue.

Author: odesenfans

.github/workflows/pytest.yml

@@ -34,6 +34,14 @@ jobs:
           echo "DYLD_LIBRARY_PATH=$(brew --prefix libsodium)/lib" >> $GITHUB_ENV
         if: runner.os == 'macOS'
 
+      # Workaround to avoid building pyobjc-core on macOS14 + Python 3.9. Support for Python 3.9 will be dropped
+      # once we support a more recent version of Python on functions.
+      - name: Avoid building pyobjc-core on macOS+Py3.9
+        if: runner.os == 'macOS' && matrix.python-version == '3.9'
+        run: |
+          echo "pyobjc-core<12" > /tmp/constraints.txt
+          echo "PIP_CONSTRAINT=/tmp/constraints.txt" >> $GITHUB_ENV
+
       - name: "Install Hatch"
         run: |
           python3 -m venv /tmp/venv