[llvm] [llvm][cmake] Quote CMAKE_CXX_COMPILER_ID in string comparison (PR #133332)

[Alex Langford via llvm-commits]

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@@ -11,7 +11,7 @@ endmacro()
 
 # MSVC and /arch:AVX is untested and have created problems before. See:
 # https://github.com/llvm/llvm-project/issues/54645
-if(${CMAKE_CXX_COMPILER_ID} STREQUAL MSVC)
+if("${CMAKE_CXX_COMPILER_ID}" STREQUAL MSVC)
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bulbazord wrote:

Based on the error message, it's likely that `CMAKE_CXX_COMPILER_ID` as a variable is empty or not defined. Expanding the variable here effectively turns this into `if(  STREQUAL MSVC)`, which is why the error complains about only seeing those two.

I would recommend changing your solution to:
`if(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")`. This makes it clear that the former is a variable and the latter is a string.

https://github.com/llvm/llvm-project/pull/133332