Recommit "Teach the default symbol vendor to respect module.GetSymbolFileFileSpec()"

This reapplies commit r351330, which was reverted due to a failing test on
macos. The failure was because the SymbolVendor used on MacOS was stricter than
the default (or ELF) symbol vendor, and rejected the symbol file because it's
UUID did not match the object file.

This version of the patch adds a uuid load command to the test macho file to
make sure the UUIDs match.

llvm-svn: 351447