Add an -object-path-prefix option to dsymutil

to remap object file paths (but no source paths) before
processing. This is meant to be used for Clang objects where the
module cache location was remapped using ``-fdebug-prefix-map``; to
help dsymutil find the Clang module cache.

<rdar://problem/55685132>

Differential Revision: https://reviews.llvm.org/D76391