7191703: jprt cannot build jdk on MacOSX. http://cr.openjdk.java.net/~ohair/openjdk8/jobjc-fix/webrev/
Fixes a partial build issue with the jdk repo on the Mac. If LANGTOOLS_DIST is defined, nothing changes and the ant script should find langtools/dist/classes.jar. Otherwise, by running ant with the import jdk, it should build ok. I very much dislike this logic but don't feel it is worth doing more than the minimum here. -kto
