[libclc] [libclc] Use custom CMake handling to overhaul libclc compilation (PR #185247)

[Wenju He via cfe-commits]

================
@@ -73,6 +75,12 @@ libclc_configure_source_list(OPENCL_SPIRV_SOURCES
   math/tanh.cl
   math/tanpi.cl
   math/tgamma.cl
+  mem_fence/fence.cl
   shared/vload.cl
   shared/vstore.cl
+  subgroup/subgroup.cl
+  synchronization/sub_group_barrier.cl
+  synchronization/work_group_barrier.cl
+  workitem/get_global_offset.cl
+  workitem/get_work_dim.cl
----------------
wenju-he wrote:

@jhuber6 oops, we probably need to revert the last commit. It adds unresolved __clc_* symbols to SPIR-V when SPIR-V backend is used and causes crash (can't handle _Z18work_group_barrierj12memory_scope call with non-constant parameters) in llvm-spirv when llvm-spirv is used.

My previous llvm-diff was wrong, it was comparing with an outdated bitcode, sorry about that.

https://github.com/llvm/llvm-project/pull/185247