Remove "buildtools" config in Makefile

[buchanae]

I added this extra "buildtools" config to the Makefile because I was getting packages showing up in the source where I didn't expect/want them, but now I understand that I just didn't have my GOPATH set up correctly. This issue is reminder for me to clean up the mess I've made and remove that "buildtools" stuff.

Notably, Go 1.8 will set a default GOPATH, so this shouldn't be as confusing for noobs like me in the future, yay. golang/go#17262