[llvm] [llvm-objdump] Fix --disassembler-color with --macho flag (PR #163815)

[James Henderson via llvm-commits]

https://github.com/jh7370 approved this pull request.

LGTM (with nit), but maybe worth getting @drodriguez to give it a quick once-over too.

https://github.com/llvm/llvm-project/pull/163815