8156989: Trailing empty element in classpath ignored

[Alan Bateman]

Martin's MineField test has been excluded for some time, one reason is 
that it exercised -Xbootclasspath/p and so doesn't work with JDK 9. Jon 
is cleaning up this test via JDK-8156989 and lo behold, it finds a 
corner case.

The corner case is where the last element of the class is the empty 
string. Long standing behavior is to treat empty elements on the class 
path as the working directory. The issue crept in because the 
implementation uses String.split and is easily fixed:
   http://cr.openjdk.java.net/~alanb/8156989/webrev/

For tests then Jon will be pushing the updated MineField to jdk9/dev 
soon. We need to go over the new options and get javac and the runtime 
consistent. I think we want it so that empty elements in the new options 
are ignored, leaving class path for legacy reasons.

-Alan.