[clang] [clang module] Current Working Directory Pruning (PR #124786)

[Steven Wu via cfe-commits]

https://github.com/cachemeifyoucan commented:

Is it better if this optimization happens really early in the process since you only visit all the options in CI? In that case, you can just reset the `CurrentWorkingDirectory` in the VFS so all the searching is done without CWD. This avoids any hard to debug issues if some options are not taken care of (needs CWD but not checked) but the trade off is more explicit errors during scanning.

https://github.com/llvm/llvm-project/pull/124786