Unsupported clang option --parallel-jobs

The use of this option here
https://github.com/GPUOpen-LibrariesAndSDKs/HIPRT/blob/main/scripts/bitcodes/compile.py#L112
and other places, causes compile errors.

This option is not available in the mainline clang, it is only available in an AMD fork.
The support of this option should be checked before its use.
