RFR (XS) 8145271 - stand-alone hotspot build is broken

[Ioi Lam]

Please review a very small fix:

    http://cr.openjdk.java.net/~iklam/jdk9/8145271-standalone-hotspot-build/

Bug: stand-alone hotspot build is broken

    https://bugs.openjdk.java.net/browse/JDK-8145271

Summary of fix:

    This was broken by the recent JDK version changes.

    The fix is to add "export" to variables such as VERSION_MAJOR so
    that they can be inherited by "make" sub processes.

Tests:

     JPRT

Thanks
- Ioi