[llvm] [offload] Add missing build dependency (PR #149326)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-offload

Author: Joachim (jprotze)

<details>
<summary>Changes</summary>

libc++ headers must be generated before compiling part of liboffload. 
The build error occurs if clang is configured to use libc++ by default. 
Fixes issue #<!-- -->149324

---
Full diff: https://github.com/llvm/llvm-project/pull/149326.diff


1 Files Affected:

- (modified) offload/tools/offload-tblgen/CMakeLists.txt (+4) 


``````````diff
diff --git a/offload/tools/offload-tblgen/CMakeLists.txt b/offload/tools/offload-tblgen/CMakeLists.txt
index 15525dc44ea60..64562fc72feac 100644
--- a/offload/tools/offload-tblgen/CMakeLists.txt
+++ b/offload/tools/offload-tblgen/CMakeLists.txt
@@ -22,5 +22,9 @@ add_tablegen(offload-tblgen OFFLOAD
   RecordTypes.hpp
   )
 
+if(TARGET cxx-headers)
+  add_dependencies(offload-tblgen cxx-headers)
+endif()
+
 set(OFFLOAD_TABLEGEN_EXE "${OFFLOAD_TABLEGEN_EXE}" CACHE INTERNAL "")
 set(OFFLOAD_TABLEGEN_TARGET "${OFFLOAD_TABLEGEN_TARGET}" CACHE INTERNAL "")

``````````

</details>


https://github.com/llvm/llvm-project/pull/149326