[clang] [clang] fix uefi target for aarch64 & x86_64 (PR #120632)

[Joseph Huber via cfe-commits]

https://github.com/jhuber6 commented:

Should probably add something to `TargetOSMacros.def` while we're at it.

https://github.com/llvm/llvm-project/pull/120632