GN: Build and link with LLD when using our Clang toolchain.

I am hoping this makes it easier to get *SAN bots going.
Today we're generating a libcompiler_rt.a that's using a
relocation type that the ld on the bots doesn't know about.
This lld is will know about anything our Clang generates.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2301273002

Review-Url: https://codereview.chromium.org/2301273002
9 files changed