[clang] [clang modules] Setting `DebugCompilationDir` when it is safe to ignore current working directory (PR #128446)

[Steven Wu via cfe-commits]

cachemeifyoucan wrote:

@adrian-prantl for the debug directory option since that might interact how debugger working with the option.

I think we need a solution approved by debugger forks for how to avoid stamping CWD into debug info and when it is safe to do so (for example, we guarantee all the paths in the TU/module are absolute path).

https://github.com/llvm/llvm-project/pull/128446