[hipcofig] Update HIP_PLATFORM detection logic
[hipcofig] Update HIP_PLATFORM detection logic

HIP_PLATFORM detection logic relied on finding a working KFD. If it was
found, the platform was set as hcc else as nvcc.
However this logic is flawed since it is possible for the development
system to only have the user mode bits to build HIP application code.
Hence the better logic is to rely on finding a suitable compiler.
The new logic is as follows:
- look for a working HCC. If found, platform is set as hcc.
- else look for a working NVCC. If found, platform is set as nvcc.
- else the platform defaults to hcc for now.

Change-Id: Ifcc42c29a19f722153d5c23c55f1a8765dceaf6b

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