[LLVM-203] Using PGO for code size optimization Communicated results and shared patch with Google Android/ChromeOs and Fuchsia teams

[LLD] Did some benchmarking of LLD against ld.bfd and ld.gold On some large applications like Mozilla and Chrome LLD can be up to 10 times faster.

Patch review and debug triage: https://bugs.llvm.org/show_bug.cgi?id=39587 https://bugs.llvm.org/show_bug.cgi?id=39571 https://reviews.llvm.org/D54314 https://reviews.llvm.org/D54145 https://reviews.llvm.org/D54265 https://reviews.llvm.org/D53980