[HIPIFY] Fix string routines.
[HIPIFY] Fix string routines.

Some Clang tooling functions return std::string, some return StringRef. Assigning of returning std::string to StringRef variables leads to garbage in it.
DEBUG build is always affected.

GPUOpen-ProfessionalCompute-Tools/HIP,GPUOpen-ProfessionalCompute-Tools/HIP,GPUOpen-ProfessionalCompute-Tools/HIP,GPUOpen-ProfessionalCompute-Tools/HIP,ROCm-Developer-Tools/HIP,ROCm-Developer-Tools/HIP,ROCm-Developer-Tools/HIP,ROCm-Developer-Tools/HIP,GPUOpen-ProfessionalCompute-Tools/HIP,ROCm-Developer-Tools/HIP