hg: build-infra/jdk8/jdk: Fix partial: JDK-8001594 Enable closed builds on Windows with Cygwin and MinGW/MSYS

[tim.bell at oracle.com]

Changeset: 74404d9c6308
Author:    tbell
Date:      2012-12-22 13:06 -0800
URL:       http://hg.openjdk.java.net/build-infra/jdk8/jdk/rev/74404d9c6308

Fix partial: JDK-8001594 Enable closed builds on Windows with Cygwin and MinGW/MSYS
Cygwin related changes.  Additional MSYS work TBD.

! make/common/shared/Defs-windows.gmk