[Driver] Save PTX files for SYCL kernels in the user input directory.

[srividya-sundaram]

Save PTX files generated (for SYCL kernels) during PTX target processing for CUDA backend using the -fsycl-dump-device-code option.

Example usage:
clang++ -fsycl -fsycl-targets=nvptx64-nvidia-cuda -fsycl-dmp-device-code=/path/to/ptx syclfile.cpp

The PTX files (.s files for each kernel) will be saved under /path/to/ptx

[jinz2014]

Thank you for the pull request.

[srividya-sundaram]

@intel/llvm-gatekeepers Hi, this is ready for merge. Thanks.

[sommerlukas]

Unrelated failures in post-commit:

Failed Tests (2):
  SYCL :: ESIMD/unified_memory_api/scatter_lacc_dg2_pvc.cpp
  SYCL :: Reduction/reduction_range_3d_rw_reducer_skip.cpp

Windows LevelZero failed with fatal: Cannot list device aspects for level_zero:gpu.