How can I make cl.exe use more cores??

I am using mscv2010 x86 here is my build steps:

@qmake.exe "C:\Users\User\QT\QT\MyPro.pro" -r -spec win32-msvc2010

jom.exe -j8 in C:\Users\User\QT\build-MyPro-Desktop_Qt_5_1_0_MSVC2010_32bit-Release@

I have the -j8 option for jom.. but it seems that it is cl.exe that is taking too much time.