[JMCInstrument] infer proper path style based on debug info

By default, the path style is decided by the host. This patch makes JMC
uses the path style used by the SP directory. This makes JMC output
host-independent.

Fixes: https://github.com/llvm/llvm-project/issues/54219

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D121236