title: In cmake, How to specific qt5 pacakge path
body: <p>When I use following code:</p>
  
  <pre><code>find_package(Qt5Widgets REQUIRED)
  add_executable(ex ex.cc)
  target_link_libraries(ex Qt5::Widgets Qt5::DBus)
  </code></pre>
  
  <p>I get:</p>
  
  <pre><code>Error:By not providing "FindQt5Widgets.cmake" in CMAKE_MODULE_PATH this project has asked CMake to find a package configuration file provided by "Qt5Widgets", but CMake did not find one.
  Could not find a package configuration file provided by "Qt5Widgets" with any of the following names:
  </code></pre>
  
  <p>My qtbase path is in "/media/roroco/disk750/Downloads/qt5/qtbase", and I have compile it, How to specific this path in <code>find_package</code></p>