SWDEV-283266 - Fix Linux Pro build for hiprtc
SWDEV-283266 - Fix Linux Pro build for hiprtc

Linux Pro build uses the LLVM_ROOT variable to
specify where llvm is located. We must use a different
name, HIP_LLVM_ROOT for LLVM's prefix location.

Change-Id: I28baf8672217a438a5dd45829d9af04b3553f615

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