RFR JDK-8061610 (XXS): "make test" broken for hotspot test targets

[David Simms]

Gidday,

Standing at the top of the JDK running "make test TEST=hotspot_all" is 
broken, there's a minor typo in "test/Main.gmk" using "JDK_OUTPUT_DIR" 
instead of "JDK_OUTPUTDIR".

Bug here: https://bugs.openjdk.java.net/browse/JDK-8061610
Patch here: http://cr.openjdk.java.net/~dsimms/8061610/

Testing: JDK JPRT and local "make test"

Cheers
/Mr. Simms