How to compile on multiple cores?

[Radagast]

Hello!
I have Qt SDK 4.6.2, and can't make my MinGW (started from QtCreator) compile a project using several cores. I've tried both setting the environment variable MAKEFLAGS=-j4 and setting -j4 as a flag to be passed to make in the project settings. Seems like mingw32-make just ignores it.
Thanks in advance.

[maropetek]

Try to use simply '-j' option.