[clang] [clang][modules] Dependency Scanning: Temporarily Turn Off Negative Directory Caching (PR #134698)

[Cyndy Ishida via cfe-commits]

cyndyishida wrote:

> This PR temporarily turns off negative directory caching to fix the build failures.

What does temporarily mean here? Is it until the project identified with errors can resolve themselves? Is it until error detection in the build system can catch cases where negative stating can cause incorrect build errors? Is it a pre-determined time frame? 

I'm concerned about disabling this optimization entirely without an understanding of how it will be turned back on. What is the added performance cost of doing this in environments where I/O accesses can be expensive? 

https://github.com/llvm/llvm-project/pull/134698