[Symbolizer] Add Build ID flag to llvm-symbolizer.

This adds a --build-id=<hex build ID> flag to llvm-symbolizer. If --obj
is unspecified, this will attempt to look up the provided build ID using
whatever mechanisms are available to the Symbolizer (typically,
debuginfod). The semantics are then as if the found binary were given
using the --obj flag.

Reviewed By: jhenderson, phosek

Differential Revision: https://reviews.llvm.org/D118633