solve the dh -Bbuild problem

solve the dh -Bbuild problem

* Add -O option, which can be used to pass options to commands, ignoring
  options that they do not support.
* dh: Use -O to pass user-specified options to the commands it runs.
  This solves the problem with passing "-Bbuild" to dh, where commands
  that do not support -B would see a bogus -u option. Closes: #541773
  (It also ensures that the commands dh prints out can really be run.)