Added .deb signing to build process; fix build issue

Reviewer: @jnealtowns 

1) Made top-level Makefile more friendly
2) Make all .deb's signed (by a default, local key, but overridable with $ONL_GNUGPHOME)
3) Fixed a build problem with the build from partially removing powerpc-as6700-32-r0b
4) Fixed a build problem with kvm (bad linked file)