Problems trying to build on Mac OSX 10.14

I need the patch from https://github.com/github/gh-ost/issues/711, so I tried to build from head. However, I had several problems. I am still picking up go, so some of these could be just misunderstandings. I can open separate issues for each if they are actually problems, but wanted to see if I was doing something wrong.
- The build scripts assume that code is checked out to `$GOPATH/src/github.com/github/gh-ost` instead of using relative paths. Perhaps this is expected in the Go world? But it would be nice to have that stated.
- The build scripts assume fpm is installed; again, undocumented, I had to find it via ruby
- Go 1.9 is incompatible with Mac OSX 10.14 (see https://github.com/golang/go/issues/25908 )
- I got `build constraints exclude all go files` when cross-compiling the linux binaries due to https://github.com/siddontang/go-mysql/issues/347