Recommit r319747 "[ELF] - Show copy relocated symbols in a --Map file output."

With fix:
Specify -soname for input dso to fix up the .dynstr section
size in different environments.

Original commit message:

As mentioned in PR35471, copied symbols did not show
in --Map output. Patch fixes that.

Differential revision: https://reviews.llvm.org/D40785

llvm-svn: 319769