RFR(XS): 8251316: Sanity check the JDK under test before running tests

[Mikael Vidstedt]

Please review this small change which adds a sanity check run of the JDK under test before running jtreg tests.

JBS: https://bugs.openjdk.java.net/browse/JDK-8251316 <https://bugs.openjdk.java.net/browse/JDK-8251316>
webrev: https://cr.openjdk.java.net/~mikael/webrevs/8251316/webrev.00/open/webrev <https://cr.openjdk.java.net/~mikael/webrevs/8251316/webrev.00/open/webrev>

* Background (from JBS)

If the JDK under test is severely broken, if for example it crashes on startup, jtreg will typically just report "Error: cannot determine version for JDK: /path/to/bin/java" without any additional information. To make it faster to diagnose the problem it would be useful to do some sanity checking of the JDK before invoking jtreg.

* Testing

I verified locally that a crashing VM does produce the expected output both on the console and in the sanity.log log file
Running tier1 now for good luck.

Cheers,
Mikael