chown your build tree to the unprivileged user, build as normal, `make
install' as root or (if you're paranoid) use `fakeroot' or some similar
package to install and then deal with the resulting miniature root tree
using GNU stow or something similar.
(Rarely (very rarely) one encounters packages that write stuff to the
build tree during the `make install' process, so you might need to be root
to *remove* it if you chose to do the final installation as root.)