Need reviewer: Fix for windows cygwin issues

[Kelly O'Hair]

Need reviewer

7012644: Regression: jdk/make/common/shared/Defs-windows.gmk has  
problems on cygwin
http://cr.openjdk.java.net/~ohair/openjdk7/jdk7-tl-cygwin/webrev/

I'm still testing builds on all platforms to make sure this is all ok.

I will push this to both the jdk7/build/jdk and jdk7/tl/jdk repository  
once it's reviewed and I'm
sure it doesn't cause any regressions to the build for RE.

-kto