Review request (s): 7116081: USE_PRECOMPILED_HEADER=0 triggers a single threaded build of the JVM

[Stefan Karlsson]

http://cr.openjdk.java.net/~stefank/7116081/webrev/

Turning off the precompiled headers is somewhat broken. It triggers a 
single threaded build even when HOTSPOT_BUILD_JOBS has been set. With 
this fix the compile times went from around 14 minutes to 2.5 minutes, 
on an 8 core machine.

This affects both Linux and BSD builds, but has only been tested on 
Linux. It would be great if someone with access to a BSD machine could 
verify this fix.