UEFI keeps regressing due to lack of CI build coverage

[linusg]

I seem to be one of the few people building for UEFI with zig master on a regular basis. It keeps being the victim of large-scale refactors so here's a tracking issue for some amount of build coverage (I'm not even asking for functionality tests).

From recent memory:

• std.debug: Fix defaultPanic() uefi build #21615
• std.os.uefi: Fix calling convention build error #21790
• Several allocators in std no longer compile #22806

[RossComputerGuy]

This is one of my plans after #22226.