Request for review: 7036525 Disable alternative source mechanism for OPENJDK builds

[David Holmes]

http://cr.openjdk.java.net/~dholmes/7036525/webrev/

Simple but crude. If OPENJDK is defined then the Hotspot "alternative 
source" mechanism is effectively disabled by checking for a non-existent 
path. This allows people using the alt-src mechanism to select which 
type of build they want in a way that is consistent with how builds of 
OPENJDK are done in the rest of the JDK.

Tested by checking the "errorReporter.cpp" location in builds 
with/without OPENJDK set, and with/without src/closed present.

This will be pushed into hotspot-rt/hotspot for hs21-b11

Thanks,
David