Add all available unix OS build tags to unix targeted Go files

https://github.com/golang/go/issues/20322 intends to eventually make this easier, and they've selected a list of build tags that unix will be an alias for: aix android darwin dragonfly freebsd hurd illumos linux netbsd openbsd solaris.

Until the unix build tag is available, I propose we add aix android darwin dragonfly freebsd hurd illumos linux netbsd openbsd solaris, regardless of whether we support or have successful builds against these target architectures. Along with this change, we can also add a make command to quickly check whether we have successful compiles against these architectures. This won't fail any build, but just provide us a quick summary.

The purpose is to allow and not block custom and unsupported builds of Runner.