[LLD] [MinGW] Print the lld-link command to stderr

This is consistent with how clang prints its internal commands with
-### and -v.

When linking with -verbose, we get log messages from the actual
linking written to stderr. By printing the command to the same stream,
we make sure they appear in a sensible chronological order.

Differential Revision: https://reviews.llvm.org/D104527