Skip compressing the macOS DMG, and drop related build steps and dependencies. Uncompressed the DMG increases from ~16mb to ~30mb, which compared to other software a user may download, (Firefox 125mb, VLC 52mb, Open Office 176mb), is still relatively small.Note that if / when we build with LTO enabled for releases, this size will shrink back down significantly again.
native_libdmg-hfsplus is not maintained, and I doubt the DMG creation feature will ever be fixed. If at some point xorrisofs supports compressing dmgs, we could enable that.
This is a backport of core#24031
This is one step needed to make the MacOS build work with the current guix script.