[libclc] [libclc] Only create a target per each compile command for cmake MSVC generator (PR #154479)

[Wenju He via cfe-commits]

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@@ -335,19 +348,28 @@ function(add_libclc_builtin_set)
     endif()
   endforeach()
 
+  set( builtins_comp_lib_tgt builtins.comp.${ARG_ARCH_SUFFIX} )
+  if ( CMAKE_GENERATOR MATCHES "Visual Studio" )
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wenju-he wrote:

> Perhaps a comment above this to explain what we're doing would be good? I see there's one above the helper function so just something brief.

done in https://github.com/llvm/llvm-project/pull/154479/commits/82c9792d38a27af0dcd789887d69fd66d7451fa0

https://github.com/llvm/llvm-project/pull/154479