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

(2) use tool "uic"
uic  hello.ui  -o  ui_hello.h

(3) build
g++  main.cpp  -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 hellodesigner

(4) run  
hellodesigner.exe