RFR 8031420: sun/management/jmxremote/bootstrap/CustomLauncherTest.java fails on some platforms: Unable to locate 'libjvm.so'

[Jaroslav Bachorik]

Please, review this small test change.

Issue : https://bugs.openjdk.java.net/browse/JDK-8031420
Webrev: http://cr.openjdk.java.net/~jbachorik/8031420/webrev.00

The test needs to check for the supported platform first and exit 
gracefully if it is run on an unsupported one.

Thanks,

-JB-