ci: Force Homebrew to overwrite the image Python

We don't care about system Python, as we use `actions/setup-python` (on
GitHub) or `UsePythonVersion` (on Azure), which install in some other
location and adjust the `PATH`. But occasionally, Homebrew will fail to
update these files because they didn't come from Homebrew, so just
silence its complaints.

Author: QuLogic

.github/workflows/tests.yml

@@ -188,7 +188,16 @@ jobs:
             ;;
           macOS)
             brew update
-            export HOMEBREW_NO_INSTALL_UPGRADE=1 HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK=1
+            # Periodically, Homebrew updates Python and fails to overwrite the
+            # existing not-managed-by-Homebrew copy without explicitly being told
+            # to do so. GitHub/Azure continues to avoid fixing their runner images:
+            # https://github.com/actions/runner-images/issues/9966
+            # so force an overwrite even if there are no Python updates.
+            # We don't even care about Homebrew's Python because we use the one
+            # from actions/setup-python.
+            for python_package in $(brew list | grep python@); do
+              brew install --overwrite ${python_package}
+            done
             brew install ccache ghostscript gobject-introspection gtk4 ninja
             brew install --cask font-noto-sans-cjk inkscape
             ;;

azure-pipelines.yml

@@ -111,7 +111,16 @@ stages:
                 ;;
               Darwin)
                 brew update
-                export HOMEBREW_NO_INSTALL_UPGRADE=1 HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK=1
+                # Periodically, Homebrew updates Python and fails to overwrite the
+                # existing not-managed-by-Homebrew copy without explicitly being told
+                # to do so. GitHub/Azure continues to avoid fixing their runner images:
+                # https://github.com/actions/runner-images/issues/9966
+                # so force an overwrite even if there are no Python updates.
+                # We don't even care about Homebrew's Python because we use the one
+                # from UsePythonVersion.
+                for python_package in $(brew list | grep python@); do
+                  brew install --overwrite ${python_package}
+                done
                 brew install --cask xquartz
                 brew install ccache ffmpeg imagemagick mplayer ninja pkg-config
                 brew install --cask font-noto-sans-cjk-sc