UB Makefile:  fix recursive make -j2

make *modules* -j2, ouch
Rework usermode PCI driver logic

- Meaningful messages about why drivers won't be built
  - State reasons drivers won't be built
  - If drivers can't be built but are explicitly requested, error out
  - If drivers can't be built but userland RT flavors requested, warn
- Check for hardy and write meaningful message
.gitattributes:  don't export git artifacts into tarball archives

This makes for a cleaner tarball for packages and releases