Backport of "Add support for Apple silicon" into 1.18

Backport of !661 (merged) "Add support for Apple silicon".

Todo:

• Needs manual intervention, cherry-picking failed!

Commits:

• 3e98d9ef macos: add support for targetting ARM64
• be3149fa ffmpeg: use Platform enums instead of strings
• 265796db ffmpeg: add support for macOS ARM64
• 103d3366 macos: add new configuration files for macos
• 4f861441 Fix Big Sur detection (was already on 1.18)
• 32cb1dcd glib: fix cross-compilation for macOS
• c13a83bc openssl: add support for macOS arm64
• 98edefa2 x264: add support for macOS ARM64
• b3b588a6 libvpx: add support for macOS ARM64
• 4095466e Add support to extract .dmg volumes
• 03e35126 gdk-pixbuf: fix files listing in cross-compilation
• dd8b650d macos: disable vulkan for ARM64