stylewindow.pro Example File
tools/styleplugin/stylewindow/stylewindow.pro
  QT += widgets
  HEADERS    = stylewindow.h
  SOURCES    = stylewindow.cpp \
               main.cpp
  TARGET     = styleplugin
  win32 {
      debug:DESTDIR = ../debug/
      release:DESTDIR = ../release/
  } else {
      DESTDIR    = ../
  }
  # install
  target.path = $$[QT_INSTALL_EXAMPLES]/widgets/tools/styleplugin
  INSTALLS += target
  CONFIG += install_ok  # Do not cargo-cult this!