[llvm] [llvm-c] Guard include of llvm-config in Visibility.h (PR #154229)

[Saleem Abdulrasool via llvm-commits]

compnerd wrote:

> For what it's worth, I am hoping for a solution where we (as in maintainers for a platform's toolchain) can continue to ship a limited set of `llvm-c` APIs based on a prebuilt non-configurable libLLVM. Adding header dependencies also adds module dependencies that I was also hoping to avoid complexity around. 

I agree with this goal. I think that the easiest way to achieve this goal is to simply ship the one extra header. This particular header is not modular, it is a textual header (though could be a standalone module I suppose),

> I was hoping that this patch would offer a reasonable middle ground where it doesn't impact preexisting workflows but still resolves our issue.

The interspersed implementation really complicates this. It would be ideal to not require the header (I had the same concerns when this change went in).

https://github.com/llvm/llvm-project/pull/154229