qmake: When calling system() it can take some time

qmake: When calling system() it can take some time, however this is a way to speed it up by utilzing the second parameter that the test function form of system has which will cause a bypass of QMakeProjectEnv. Therefore, it would be nice if there was a third parameter added to the replace form of system() which would do the same thing as the test function form of system() in this respect.