Multicore compilation with Qt 5.1 and jom on Windows 7 failed

Multicore compilation with Qt 5.1 and jom on Windows 7 failed

I have installed Qt 5.1.1 with MinGW 4.8 and QtCreator through Qt Online
installer. I launched Qt creator and made new project (Qt application
Desktop) with MainWindow class based on QMainWindow (default). It works
fine and popped up a mainwindow after compilation.
However, when I used C:\Qt\Qt5.1.1\Tools\QtCreator\bin\jom.exe instead of
C:\Qt\Qt5.1.1\Tools\mingw48_32\bin\mingw32-make.exe , I got some output
like below.
jom 1.0.13 - empower your cores
C:\Qt\Qt5.1.1\Tools\QtCreator\bin\jom.exe -f Makefile.Release
g++ -c -pipe -fno-keep-inline-dllexport -O2 -frtti -Wall -Wextra
-fexceptions -mthreads -DUNICODE -DQT_NO_DEBUG -DQT_WIDGETS_LIB
-DQT_GUI_LIB -DQT_CORE_LIB -DQT_NEEDS_QMAIN -I../foobar
-I'C:/Qt/Qt5.1.1/5.1.1/mingw48_32/include'
-I'C:/Qt/Qt5.1.1/5.1.1/mingw48_32/include/QtWidgets'
-I'C:/Qt/Qt5.1.1/5.1.1/mingw48_32/include/QtGui'
-I'C:/Qt/Qt5.1.1/5.1.1/mingw48_32/include/QtCore' -I'release' -I'.' -I'.'
-I'C:/Qt/Qt5.1.1/5.1.1/mingw48_32/mkspecs/win32-g++' -o release/main.o
../foobar/main.cpp
In file included from ../foobar/main.cpp:1:0:
../foobar/mainwindow.h:4:23: fatal error: QMainWindow: No such file or
directory
#include <QMainWindow>
^
compilation terminated.
jom:
D:\work\build-foobar-Desktop_Qt_5_1_1_MinGW_32bit-Release\Makefile.Release
[release\main.o] Error 1
jom: D:\work\build-foobar-Desktop_Qt_5_1_1_MinGW_32bit-Release\Makefile
[release] Error 2
15:17:38: Process "C:\Qt\Qt5.1.1\Tools\QtCreator\bin\jom.exe" stopped with
code 2
Error while building/deploying project foobar (kit: Desktop Qt 5.1.1 MinGW
32bit)
During step 'Make'
15:17:38: Elapsed time: 00:00.
My .pro is like this.
#-------------------------------------------------
#
# Project created by QtCreator 2013-09-08T15:16:13
#
#-------------------------------------------------
QT += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = foobar
TEMPLATE = app
SOURCES += main.cpp\ mainwindow.cpp
HEADERS += mainwindow.h
FORMS += mainwindow.ui
I think the line in .pro greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
and in the output during compilation
-I'C:/Qt/Qt5.1.1/5.1.1/mingw48_32/include/QtWidgets' looks fine, but
failed.
How can I compile with Qt 5.1 and jom on Windows 7 (32 bit)?
Thanks in advance.