CI: Update system path for coveralls on macOS

Apparently on macOS, there can be multiple versions of `coveralls`, one
from the github action, and one from a python package. The action gets
confused of which one to pick, most certainly it is the one that does
not work and the macOS jobs fail.

Updates the $PATH environment variable to put the homebrew version
first to fix that.

.github/workflows/ci_build_and_test.yml

@@ -74,6 +74,12 @@ jobs:
       - name: Upload coverage report
         uses: codecov/codecov-action@v3
 
+      - name: Update path for macOS
+        # Updates $PATH so that `coveralls` does not get confused with the
+        # locally installed python package
+        if: startsWith(runner.os, 'macOS')
+        run: echo "/opt/homebrew/bin" >> $GITHUB_PATH
+
       - name: Upload to Coveralls
         uses: coverallsapp/github-action@v2
         with: