feat: add support for multi-arch repositories

[gaige]

• added support for multi-arch repositories
• manually set os to ‘linux’ as there are (at least for now) no ‘smartos’ docker images

[danmcd]

See TritonDataCenter/smartos-live#1143 in case it helps.

[cneira]

@gaige, I added your work in #45. I added a couple of changes, but all tests are passing now(let me know if you are ok with that) I added you as the author and myself as the coauthor.

[gaige]

@gaige, I added your work in #45. I added a couple of changes, but all tests are passing now(let me know if you are ok with that) I added you as the author and myself as the coauthor.

Works for me. I'm all about the fastest way to get this into the code base :-)