[clang] [Clang][Solaris] Support --ld-path in Solaris driver (PR #163000)

[Daniel Levin via cfe-commits]

daniel-levin wrote:

> with -fuse-ld=, /usr/bin/ld is invoked and and -z relax=transtls should be passed as checked using the CHECK-LD-X64-UBSAN  label.

I mean sure, we could replicate this behavior, but I don't think that is a sensible behavior. Why on earth would blank `fuse-ld=` revert to using Solaris LD when clang was explicitly built to use GNU ld? I'm not off base in thinking this is a violation of the least surprise principle, am I?

https://github.com/llvm/llvm-project/pull/163000