Write new tests for r362121

Summary:
The tests for r362121 ran dsymutil against a test binary every time.
This caused problems on lld-x86_64-ubuntu-fast as dsymutil required
a lipo tool be available to process those binaries.

This change rewrites the new test cases in macho-disassemble-g-dsym
to use bespoke test binaries (exe and dwarf) simplifying the test's
runtime dependencies.

The changes to tools/llvm-objdump/MachODump.cpp are unchanged from
r362121

Reviewers: pete, lhames, JDevlieghere

Reviewed By: pete

Subscribers: smeenai, aprantl, rupprecht, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D62694

llvm-svn: 362141