[dsymutil] Add -verify option to run DWARF verifier after linking.

This patch adds support for running the DWARF verifier on the linked
debug info files. If the -verify options is specified and verification
fails, dsymutil exists with abort with non-zero exit code. This behavior
is *not* enabled by default.

Differential revision: https://reviews.llvm.org/D40777

llvm-svn: 320033