[compiler-rt] [compiler-rt][MSVC][CMake] Wrap Linker flags for ICX (PR #118496)

[via llvm-commits]

BukeBeyond wrote:

> I don't think compiler-rt ever compiled cleanly when using `clang` (instead of `clang-cl`) on Windows. It is as the rest of LLVM not tested this way. @BukeBeyond I would encourage you to figure out why the runtimes build is being set up this way, instead of trying to fix compiler-rt with clang.

Thank you for your diligence on the matter!

At LLVM 18 and 19, I was using able to build clang, clang-tools-extra and compiler-rt with just clang on windows.  In 20 and 21, most executables built, but clangd would run and but crash in vs code.  Also the Clspv project, which is heavily based on LLVM, the debug builds were fine, but in the release build, clspv.exe would crash right away (during global variable construction).

We wish LLVM became more independent of MS tools, and would be able to build itself on windows using just clang and lld-link.  But that is not the case in V20+.  I have tried to replicate the major internal flags of of clang-cl for clang, but have not succeeded yet.

https://github.com/llvm/llvm-project/pull/118496