LLVMFlang: Add support for targeting MSVC ABI on Windows
The compiler does not yet support everything needed to integrate well with the MSVC ABI, in particular for runtime library selection and debug format selection. Document them in FIXME comments and leave this support undocumented by CMake for now.
Fixes: #24840 (closed)
Inspired-by: @pbo-linaro
Backport: release
Supersedes: !8776 (closed)
Edited by Brad King