[compiler-rt] [compiler-rt][MSVC] Update check to include clang-cl (PR #150108)

[Eli Friedman via llvm-commits]

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@@ -594,8 +594,8 @@ set(aarch64_SOURCES
   aarch64/fp_mode.c
 )
 
-# Append sources specific to AArch64 targets that aren't supported by MSVC.
-if(NOT MSVC)
+# Append sources specific to AArch64 targets that aren't supported by cl.exe
+if(CLANG_CL OR NOT MSVC)
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efriedma-quic wrote:

It's set by llvm/cmake/modules/CheckCompilerVersion.cmake.

But I don't think it's the right thing, in any case.  The issue here isn't whether you're using a compiler in cl emulation mode, the issue is that Windows COFF requires different assembler directives.  The correct check for that is something like `WIN32 OR CYGWIN`.

https://github.com/llvm/llvm-project/pull/150108