[CMake][ELF] Remove lld 13 workaround for gc-sections now that #72061 was merged

[finagolfin]

@al45tair, one last build flag cleanup after your pull eliminating the need for this workaround.

[finagolfin]

@kateinoigakukun, please run the CI.

[kateinoigakukun]

Nice

[kateinoigakukun]

@swift-ci test

[finagolfin]

Hmm, the build log says -- GNU Gold is too old (2.34); using lld instead and since the host tools are still built with Swift 5.8.1 without the trunk ELF fix, lld cannot link with gc-sections and fails.

@al45tair, was it intentional to switch the linux CI over to using lld now or did this just happen without your knowing it, because of that CMake logic? Either way, we may have to wait on removing this flag until the prebuilt host toolchain on the linux CI has your ELF fix.

[al45tair]

Gah. I made that change while trying to resolve the previous LLDB problems; it fixed one problem but it wasn't sufficient, so I had to fix the underlying problem in LLDB itself anyway. I left it in because it seemed like not a bad idea given that we're now shipping lld with the toolchain, but if it's a problem we could just disable that code for now (maybe it could just warn that you're using an old version of Gold, rather than changing to using LLD?)

[finagolfin]

It's no problem at all: I'm all for the switch to lld and Evan is planning to defer to whatever linker clang uses, swiftlang/swift-driver#1595.

I simply did not know that the linux CI had switched to lld, plus I always build the trunk toolchain for Android with the latest prebuilt trunk toolchain for linux, so I figured we could get rid of this flag.

However, we do support building the compiler with older toolchains, so best to put this on ice till your fix makes it into the prebuilt toolchain on the linux CI, marking this pull as draft till then.