[clang] [Driver] Add toolchain for X86_64 UEFI target (PR #76838)

[Pranav Bhandarkar via cfe-commits]

bhandarkar-pranav wrote:

> Looks like this breaks tests on Mac: http://45.33.8.238/macm1/92471/step_6.txt
> 
> Please take a look and revert for now if it takes a while to fix.
@nico 
I cannot access the link from my work VPN, but if this is the issue (https://github.com/llvm/llvm-project/issues/109328) then here is a fix (https://github.com/llvm/llvm-project/pull/109329) 

https://github.com/llvm/llvm-project/pull/76838