Rollup merge of #87320 - danakj:debug-compilation-dir, r=michaelwoerister

Rollup merge of #87320 - danakj:debug-compilation-dir, r=michaelwoerister

Introduce -Z remap-cwd-prefix switch

This switch remaps any absolute paths rooted under the current
working directory to a new value. This includes remapping the
debug info in `DW_AT_comp_dir` and `DW_AT_decl_file`.

Importantly, this flag does not require passing the current working
directory to the compiler, such that the command line can be
run on any machine (with the same input files) and produce the
same results. This is critical property for debugging compiler
issues that crop up on remote machines.

This is based on adetaylor's https://github.com/rust-lang/rust/commit/dbc4ae7cba0ba8d650b91ddd459b86a02a2d05c5

Major Change Proposal: https://github.com/rust-lang/compiler-team/issues/450
Discussed on #38322. Would resolve issue #87325.