Add /reproduce option to lld/COFF

This patch adds /reproduce:<path> option to lld/COFF. This is an
lld-specific option, so we can name it freely. I chose /reproduce
over other names (e.g. /lldlinkrepro) for consistency with other lld
ports.

Differential Revision: https://reviews.llvm.org/D68381

llvm-svn: 373704