pgbuildfarm - client-code: provide for file flag to force one run.

Log Message:
-----------

provide for file flag to force one run. useful so you don't have to
mangle crontabs.

Modified Files:
--------------
client-code:
run_build.pl (r1.60 -> r1.61)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbuildfarm/client-code/run_build.pl.diff?r1=1.60&r2=1.61)