Only run vector generation once at the end of make invocation

[Rahix]

Maybe someone else has better GNU make skills than I have: Right now, the GEN-VECTOR step runs once for each chip. It would be better to only run it a single time after all other jobs have completed. Is there a way to do that?

[Rahix]

This becomes superfluous with #157 on the horizon. Will close this issue once that PR is merged.