Fix lint error in parallel processing.

Fix lint error in parallel processing.

gyp.input fails the presubmit lint check because of an uninitialised global.
The last rewrite of the parallel processing CL eliminated the need for this to
be global, so just remove the global declaration.
Committed: https://code.google.com/p/gyp/source/detail?r=1515

[Torne, 2012-10-04 11:15:14]

Hi Dominic, this is a fix for your parallel processing code to make it pass the
gyp presubmit check :)

[dmazzoni, 2012-10-04 16:50:26]

lgtm