Don't pass the `-i` flag to go when building

[defuse]

└─ $ make
GO111MODULE=on CGO_ENABLED=1 go build -i -v ./cmd/server

Linda ran into https://github.com/golang/go/issues/37962 which is happening because I think the -i flag means install dependencies to the system, or something like that.

I don't see how that command is actually generated from the Makefile at the moment but we probably don't want the -i in there.

[lindanlee]

@defuse I don't think I'll be looking at this, could you see if you can fix it?

[lindanlee]

I'm currently just removing the -i flags locally and everything seems to be fine. Not sure if it'll break things for other OSes if they are just removed outright.