[llvm] [offload] Add `dlwrap::loaded` function to check for optional symbols (PR #210737)

[via llvm-commits]

================
@@ -8,7 +8,13 @@ target_compile_definitions(omptarget.rtl.cuda PRIVATE OFFLOAD_MIN_CUDA_VERSION=$
 
 find_package(CUDAToolkit QUIET ${OFFLOAD_MIN_CUDA_VERSION})
 
-if(CUDAToolkit_FOUND AND NOT "cuda" IN_LIST LIBOMPTARGET_DLOPEN_PLUGINS)
+if (WIN32 AND NOT "cuda" IN_LIST LIBOMPTARGET_DLOPEN_PLUGINS)
----------------
blazej-smorawski wrote:

Yes we could, but then I think it's likely that we will forget about updating the check when we add a new plugin, because we would have to check if LIBOMPTARGET_DLOPEN_PLUGINS contains plugin A,B,C,D right?

https://github.com/llvm/llvm-project/pull/210737