Modified (txnid2's) run.sh's function bigjars to, before generating (#6857)
Modified (txnid2's) run.sh's function bigjars to, before generating (#6857)

* Modified (txnid2's) run.sh's function bigjars to, before generating new java jar
files, besides checking the current directory (which it already does), also check
certain other directories, based on the VOLTDB_BASE environment variable; and if
found, then copy them from there.
* Call the bigjars function only when the BIGJARS environment variable is set
(to a nonempty string).
VoltDB/voltdb,VoltDB/voltdb,VoltDB/voltdb,VoltDB/voltdb,VoltDB/voltdb,VoltDB/voltdb,VoltDB/voltdb