kpatch-build is outgrowing the kpatch script and probably is a better
fit as its own utility instead of being wrapped by kpatch. Install
kpatch-build into /usr/local/bin, remove the kpatch wrapper around it,
and update the README accordingly.
- setup the makefiles to support "make" and "make install", which builds
the kpatch-build tools and installs everything in /usr/local.
- update kpatch-build to support new paths
- add "kpatch build" wrapper around kpatch-build