[8u60] Request for approval for 8066808 langtools/test/Makefile should not use OS-specific jtreg binary

[Roger Riggs]

Please approve the backport of the change to invoke jtreg without the 
platform.
It was made to 9 and has been backported to 7 but not 8.

Changeset:
http://hg.openjdk.java.net/jdk9/jdk9/langtools/raw-rev/2b47c42974ff

Original Issue:
    https://bugs.openjdk.java.net/browse/JDK-8066808

Thanks, Roger