Only run Makefile during build phase (not install)

Currently, `Makefile` is re-run when catkin installs the package. This causes `Makefile` to re-install, this time leaving the files in `/` instead of an intermediate directory. This patch ensures that once built, `Makefile` is not re-run.

There are currently a bunch of files being installed to `/` in Fedora and probably in Ubuntu, too.