Use gold as the linker on Linux

[jakepetroules]

Doesn’t seem like using lld really works, so we need to use gold. This is also the status quo for Linux builds since swift-driver will pass -fuse-ld=gold if used as linker driver.

[al45tair]

Curious to know what the problem was with lld. There are community members pushing for more use of lld, and some Linux distros only have lld installed by default too.

[jakepetroules]

@neonichu might remember more details as to the specific issues here.

[neonichu]

Unfortunately, I don't remember, what I noted down at the time was this:

Some more info here: https://forums.swift.org/t/building-the-swift-project-on-linux-with-lld-instead-of-gold/73303/7

I think the problem I was running into is relocating protected symbols, so I guess we are currently using BFD

So I am assuming I was running into some of the problems described in that thread, but wasn't sure myself what it was concretely.

[compnerd]

I think that we should favour the system linker - gold is now officially deprecated, and BFD is able to link the swift libraries. We should transition back towards using the system linker and let the Linux distribution decide whether that should be gold, bfd, or lld (or even mold or wild). Continuing to use clang as the linker driver basically means that all we need to do is drop the -use-ld=... and -fuse-ld=... flags from being added.

[jakepetroules]

@compnerd Seems reasonable. I copied this issue from a list we'd come up with a while back, so it's likely based on outdated observations.