[8u40] approval request for 8061257: nashorn ant build script should have a sanity target

[A. Sundararajan]

Please approve.

Bug: https://bugs.openjdk.java.net/browse/JDK-8061257
jdk8 webrev: http://cr.openjdk.java.net/~sundar/8061257/8u40/webrev.00/
jdk9 review thread: 
http://mail.openjdk.java.net/pipermail/nashorn-dev/2014-October/003686.html

Fix is backported "as is" without any jdk8 specific changes. No 
regression test as this is a build script change. Added noreg-build 
label to the bug.

Thanks,
-Sundar