qtCompile function fail when jom is used with '-j' flag specified.

I was building Qt 5.2.1 from source and used jom tool instead of standard nmake. I used instructions from "Building Qt5 from Git" site and run 'configure' script to build all components.

However, when I run 'jom -j8' command, all qtmultimedia tests fail because of "NMAKE : fatal error U1065: invalid option 'j'" errors. Probably more modules are affected by this bug, but this was the one that I noticed.