Fix macOS build in GitHub Actions

[letmaik]

The build of glib (dependency of libraw) is failing in CI like this:

Program python3 (packaging) found: NO
../meson.build:2383:26: ERROR: python is missing modules: packaging

The packaging package is installed in the venv of the Python from https://github.com/multi-build/multibuild.git as part of build-macos.sh. It's not clear why this is failing. It started happening when bumping the build agent from macos-11 to macos-12.

This issue is currently blocking a new release that depends on numpy 2.