Implement -r mode for the Mach-O linker.

What's Changed

• wasm - fix debug info & misc by @Luukdegram in https://github.com/kubkon/zld/pull/96
• macho: implement -r mode by @kubkon in https://github.com/kubkon/zld/pull/95
• macho: write data-in-code entries in -r mode by @kubkon in https://github.com/kubkon/zld/pull/99
• macho+test: misc fixes by @kubkon in https://github.com/kubkon/zld/pull/100

Full Changelog: https://github.com/kubkon/zld/compare/v0.0.3...v0.0.4