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