Handle KeyboardInterrupt in Buck build wrapper scripts

Pressing Ctrl-C during the build results in an ugly Python
TraceBack.

Add handling of KeyboardInterrupt and print a useful message.

This fixes most cases, but there are still a few TraceBacks
coming from inside Buck.  These will need to be fixed upstream.

Change-Id: I3f0dc19f3be599460a2a6409642a70a195b50753
2 files changed