[llvm] [openmp] [OpenMP][Offload] Support standalone build (PR #88957)

[Joseph Huber via llvm-commits]

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@@ -214,6 +226,31 @@ set(LIBOMPTARGET_GPU_LIBC_SUPPORT ${LLVM_LIBC_GPU_BUILD} CACHE BOOL
     "Libomptarget support for the GPU libc")
 pythonize_bool(LIBOMPTARGET_GPU_LIBC_SUPPORT)
 
+if(OPENMP_STANDALONE_BUILD)
+  if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
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jhuber6 wrote:

Don't we already do `find_package(LLVM)` somewhere else? And why only Clang.

https://github.com/llvm/llvm-project/pull/88957