Makefile: use `go get` instead of `go install` to install packages
Makefile: use `go get` instead of `go install` to install packages

elves/elvish,CodyGuo/elvish,CodyGuo/elvish,ke7ofi/elvish,elves/elvish,ke7ofi/elvish,elves/elvish,beni55/elvish,elves/elvish,elves/elvish,beni55/elvish