[9] Review Request: 8151288 Generation of property files for gtk l&f can be skipped on win/osx

[Sergey Bylokhov]

Hello,
Please review the small fix for jdk9.
  In the fix for JDK-8075277 [1] we removed gtk l&f on osx, but its 
property files still generates (but actually are not used during the build).
"PROP_SRC_DIRS" is a list of folders where the property files should be 
searched.

[1] https://bugs.openjdk.java.net/browse/JDK-8075277

Bug: https://bugs.openjdk.java.net/browse/JDK-8151288
Webrev can be found at: http://cr.openjdk.java.net/~serb/8151288/webrev.00

-- 
Best regards, Sergey.