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

[Tobias Hieta via llvm-commits]

tru wrote:

I can, but I wasn't sure we usually tested error strings. Guess I was under the impression that we had tests for the error condition. I'll look into it tomorrow.

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?

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