Created by: dpursehouse
Summary: Terminating a buck build with CTRL-C sometimes results in a Python Traceback being shown on the terminal.
Fix this by catching KeyboardInterrupt in the main() method. Don't do anything with the caught exception; just pass.
Test Plan: Build something. Terminate it with CTRL-C. Don't see a TraceBack.
Change-Id: I3e84d7056c43df0db7a2acf7fd8aed7472d058ce