[clang] [clang] Add a CodeGen option to ignore compilation directories (PR #149897)

[David Blaikie via cfe-commits]

dwblaikie wrote:

> Here is idea to not to add a new option. I am going to remove the fallback in CodeGen but make sure clang-driver does the fallback computation and clang cc1 will always respect that decision from clang-driver. In that case, it is a behavior change for cc1 flag, but not for a driver flag.

& then for now, in your use case, you'd be using the cc1 flag via -Xclang, etc? I think that changing the driver to have the smarts there, but having cc1/frontend just respect whatever it's given sounds good to me, if a little subtle for now - but nothing drastic.

https://github.com/llvm/llvm-project/pull/149897