This serves as an alternative to Homebrew. It should be much more stable
and cause less headaches over time for automated builds.
There should be no change to the end user experience of using the build
script, as it should still work with and use Homebrew by default.
Additionally, Nix provides older Apple SDKs, allowing us to run against
macOS 11.x SDKs. This allows the resulting Emacs.app builds to be
compatible with macOS 11.x and later versions.
In testing, this seems to be the case on macOS 11.x (x86_64) and macOS
12.x (arm64).
The sign command signs Emacs.app application bundles with Apple's
codesign utility.
It does a few things outside of just executing codesign:
- Is aware of *.eln native-compilation files, which need to be
explicitly searched for on disk and passed to codesign, as they are
not detected when using the "--deep" option.
- Is aware of Contents/MacOS/bin/emacs CLI helper tool which we add into
the application bundle, and specifically passed it to codesign as
well.
- By default provides a set of entitlements which are relevant for Emacs
when running codesign.
