[llvm] [Offload] Fix CMake detection when it is not found (PR #90729)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-offload

Author: Joseph Huber (jhuber6)

<details>
<summary>Changes</summary>

Summary:
This variable could be unset if not found or when building standalone.
We should check for that and set it to true or false.

Fixes: https://github.com/llvm/llvm-project/issues/90708


---
Full diff: https://github.com/llvm/llvm-project/pull/90729.diff


1 Files Affected:

- (modified) offload/CMakeLists.txt (+6-1) 


``````````diff
diff --git a/offload/CMakeLists.txt b/offload/CMakeLists.txt
index a416ac29873f4f..42e0f5740f116d 100644
--- a/offload/CMakeLists.txt
+++ b/offload/CMakeLists.txt
@@ -302,7 +302,12 @@ endif()
 
 pythonize_bool(LIBOMPTARGET_OMPT_SUPPORT)
 
-set(LIBOMPTARGET_GPU_LIBC_SUPPORT ${LLVM_LIBC_GPU_BUILD} CACHE BOOL
+if(${LLVM_LIBC_GPU_BUILD})
+  set(LIBOMPTARGET_HAS_LIBC TRUE)
+else()
+  set(LIBOMPTARGET_HAS_LIBC FALSE)
+endif()
+set(LIBOMPTARGET_GPU_LIBC_SUPPORT ${LIBOMPTARGET_HAS_LIBC} CACHE BOOL
     "Libomptarget support for the GPU libc")
 pythonize_bool(LIBOMPTARGET_GPU_LIBC_SUPPORT)
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/90729