[ITP] lld

[Jeremy Drake]

LLD is a linker from the LLVM project that is a drop-in replacement for
system linkers and runs much faster than them. It also provides features
that are useful for toolchain developers.

Current packaging is in the playground repository, on the lld branch.
https://cygwin.com/cgit/cygwin-packages/playground/tree/?h=lld&id=d7936632fa8e96bc43a15d4c6598595767e33bb3

This depends on the updated llvm package, so can't really be built without
that whole stack.  It does still need work to be usable for a Cygwin
target, but works well for cross-compilation to mingw at least, and
probably other targets as well.

Current test results:

Total Discovered Tests: 1066
  Unsupported:   10 (0.94%)
  Passed     : 1056 (99.06%)