hip-config.cmake - resolve HIP_CLANG_ROOT when the compiler is a symlink

When the HIP compiler set to a symblink that was created outside
/opt/rocm/llvm/bin, HIP's cmake would get HIP_CLANG_ROOT incorrectly.
This teaches hip-config to get clang's real path first and use that to determine LLVM's directory.

Change-Id: I6275b67f843aff256dc72cf478e575224e0cedc3

hipamd/hip-config.cmake.in

@@ -151,8 +151,9 @@ if(HIP_COMPILER STREQUAL "clang")
       get_filename_component(HIP_CLANG_ROOT "${CMAKE_MATCH_1}" DIRECTORY)
     endif()
   elseif (HIP_CXX_COMPILER MATCHES ".*clang\\+\\+")
-    get_filename_component(HIP_CLANG_ROOT "${HIP_CXX_COMPILER}" DIRECTORY)
-    get_filename_component(HIP_CLANG_ROOT "${HIP_CLANG_ROOT}" DIRECTORY)
+    get_filename_component(_HIP_CLANG_REAL_PATH "${HIP_CXX_COMPILER}" REALPATH)
+    get_filename_component(_HIP_CLANG_BIN_PATH "${_HIP_CLANG_REAL_PATH}" DIRECTORY)
+    get_filename_component(HIP_CLANG_ROOT "${_HIP_CLANG_BIN_PATH}" DIRECTORY)
   endif()
   file(GLOB HIP_CLANG_INCLUDE_SEARCH_PATHS ${HIP_CLANG_ROOT}/lib/clang/*/include)
   find_path(HIP_CLANG_INCLUDE_PATH stddef.h