[clang] uefi_cxx_abi (PR #150115)

[Prabhu Rajasekaran via cfe-commits]

Prabhuk wrote:

> looks ok to me. Or do you think it would make more sense to put this check in `isKnownWindowsMSVCEnvironment()`?

Thanks Amy! We want to make decisions for UEFI environment without MSVC/windows assumptions. It was one of the motivations for introducing the UEFI target triple. So I am not modifying the definition of `isKnownWindowsMSVCEnvironment` to include UEFI. 


https://github.com/llvm/llvm-project/pull/150115