Use system clang.

Forwarded: not yet.

Index: clang-ocl-rocm-5.0.2/CMakeLists.txt
===================================================================
--- clang-ocl-rocm-5.0.2.orig/CMakeLists.txt
+++ clang-ocl-rocm-5.0.2/CMakeLists.txt
@@ -20,7 +20,7 @@ if(hcc_FOUND)
     set(CLANG_BIN "${hcc_LIB_INSTALL_DIR}/../bin" CACHE STRING "")
     set(BITCODE_DIR "${hcc_LIB_INSTALL_DIR}" CACHE STRING "")
 else()
-    find_program(CLANG_EXE NAMES clang HINTS ${CXX_COMPILER_PATH}/bin PATHS /opt/rocm/llvm/bin)
+    find_program(CLANG_EXE NAMES clang)
     get_filename_component(CLANG_EXE_DIR ${CLANG_EXE} DIRECTORY)
     find_package(AMDDeviceLibs PATHS /opt/rocm)
     set(CLANG_BIN "${CLANG_EXE_DIR}" CACHE STRING "")