[llvm] [Support] Better error msg when cache dir can't be created. (PR #69575)

[Tobias Hieta via llvm-commits]

tru wrote:

> > what do you think about the fact that it calls a fatal error here? Wouldn't a normal error be enough so that you don't get a scary trace back just for a missing directory?
> 
> I don't think the caching code itself is reporting it as a fatal error, it is simply returning an error from localCache() and I guess the linker client is reporting as a fatal error? I'm not sure what the linker typically does for errors like this.

That's true, the fatal error actually comes from the LTO backend:

https://github.com/llvm/llvm-project/blob/main/llvm/lib/LTO/LTOBackend.cpp#L407



https://github.com/llvm/llvm-project/pull/69575