parallelize the launching of $OPTICHARGER form squiasher script

Before

real    1m25.583s
user    1m14.101s
sys     0m21.717s

After

real    0m47.257s
user    1m46.123s
sys     0m23.453s

Change-Id: I1ca0013f8dec9175027f2e9bed93786cfe3804d5

tools/squisher

@@ -76,7 +76,7 @@ echo
 cd $REPACK/ota/system/framework
 $OPTICHARGER framework-res.apk
 cd $REPACK/ota/system/app
-for i in *.apk; do $OPTICHARGER $i; done
+find ./ -name \*.apk | xargs  --max-args=1 --max-procs=`grep 'processor' /proc/cpuinfo | wc -l`  $OPTICHARGER
 )