[lld] [LLD][MinGW] Support machine:arm64x when invoked in MinGW mode. (PR #145343)

[Jacek Caban via llvm-commits]

https://github.com/cjacek approved this pull request.

The change looks fine to me.

FWIW, the MinGW-specific parts should mostly be fine on the lld-link side. There are probably some nuances that will need to be addressed. For example, `-alternatename` only applies to the EC symbol table, so the `__image_base__` alias will likely need a different approach.

The main remaining challenge for setting up a fully ARM64X-compatible MinGW toolchain is how static and import libraries are distributed. On MSVC, they’re provided as hybrid archives, which eliminates ambiguity: the linker just finds one file and pulls in both sets of symbols. Replicating this with MinGW will require a fair bit of build system work, mostly on the mingw-w64-crt side.

https://github.com/llvm/llvm-project/pull/145343