Populate HIP_CLANG_PATH if its not declared
Populate HIP_CLANG_PATH if its not declared

Change-Id: Ibc1f2e9b3389b6cc7a58579cfb293999ad6e9398

ROCm-Developer-Tools/HIP,ROCm-Developer-Tools/HIP,ROCm-Developer-Tools/HIP,ROCm-Developer-Tools/HIP,ROCm-Developer-Tools/HIP