RFR: JDK-8009819 build-infra: RE jdk8 build forest fails for windows since addition of --with-dxsdk

[Tim Bell]

Please review this change, which provides a fallback to the traditional 
location for the DXSDK if it is not specified on the configure line.  We 
don't like doing this, but in this case I will give in.  It seems many 
of the legacy build systems we use internally do not have the 
environment variable defined.

Bug report (not visible externally yet... should be soon):

     http://bugs.sun.com/view_bug.do?bug_id=8009819

JDK-8009819
build-infra: RE jdk8 build forest fails for windows since addition of 
--with-dxsdk

Webrev:

    http://cr.openjdk.java.net/~tbell/8009819/webrev.00/


This is related to the fix for 8008073, which is still in the build forest.

     http://bugs.sun.com/view_bug.do?bug_id=8008073

Thank you-

Tim