[PATCH] Always add LLVMgold.so plugin if it's present in the standard location

[Rafael Espíndola]

> Yeah, it looks like ld errors if it's given a bad option. So, having
> this as the default won't work smoothly in all cases.
>
> What if this were hidden behind a build flag that defaulted to OFF?
> I.e., you can choose to build a version of clang that always passes
> gold to ld, but the default would stay the way it currently is.

That is probably fine. Note that we always try to make llvm and clang
build options be just the default value of a runtime option. Not sure
if that would be strictly needed in here since the compile time option
would just be what -flto is during link time.

>>
>> What is the performance impact of passing -plugin when no LTO is being done?
>
> This is a good question, and I'm going to try it out on some large
> codebases soon.

Thanks!

Cheers,
Rafael