RFR: 8080758 test/lib/Makefile leaves artifacts in the source tree

[Ingemar Aberg]

Hi,

Please review this change of test/lib/Makefile

New features:
1) allow the Makefile to put artifacts/temporaries in a user-specified 
directory instead of in the source tree
2) split the build directories to allow parallel builds without risking 
one target messing with files used by another

bug: https://bugs.openjdk.java.net/browse/JDK-8080758

webrev: http://cr.openjdk.java.net/~iaberg/JDK-8080758/main.00/

/Ingemar