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

[tim.bell at oracle.com]

Changeset: cf34c0055572
Author:    tbell
Date:      2012-12-28 02:20 -0800
URL:       http://hg.openjdk.java.net/build-infra/jdk8/jdk/rev/cf34c0055572

Fix partial: JDK-8001594 Enable closed builds on Windows with Cygwin
export EXTRA_COMP_PATH and use it when bulding in install

! make/common/Defs-windows.gmk