(1) enter
cd /d D:\QtProjects\ch02\helloqt

(2) build
g++  helloqt.cpp   -std=c++0x  -I"C:\Qt\Qt5.4.0\5.4\mingw491_32\include"  -L"C:\Qt\Qt5.4.0\5.4\mingw491_32\lib" -lQt5Core -lQt5Gui -lQt5Widgets  -o helloqt

(3) run 
D:\QtProjects\ch02\helloqt\helloqt.exe