title: Updated Qt library; cannot build anymore
body: <p>I have a previously working Qt5/cmake project which built fine. I then updated Qt from 5.6 to 5.8. Now cmake cannot find Qt anymore. </p>
  
  <p>This is my <code>CMakeLists.txt</code> file:</p>
  
  <pre><code>cmake_minimum_required(VERSION 3.0)
  project(TEST)
  set(CMAKE_INCLUDE_CURRENT_DIR ON)
  
  set(CMAKE_PREFIX_PATH "/opt/Qt/Qt5.8.0")
  set(QT_QMAKE_EXECUTABLE ${CMAKE_PREFIX_PATH}/5.8/clang_64/bin/qmake)
  
  find_package(Qt5Widgets)
  ...
  </code></pre>
  
  <p>This is the error message I get:</p>
  
  <pre><code>CMake Warning at CMakeLists.txt:56 (find_package):
    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:
  
      Qt5WidgetsConfig.cmake
      qt5widgets-config.cmake
  
    Add the installation prefix of "Qt5Widgets" to CMAKE_PREFIX_PATH or set
    "Qt5Widgets_DIR" to a directory containing one of the above files.  If
    "Qt5Widgets" provides a separate development package or SDK, be sure it has
    been installed.
  </code></pre>
  
  <p>I followed what written in <a href="http://doc.qt.io/qt-5/cmake-manual.html" rel="nofollow noreferrer">Qt documentation</a>, so I do not understand what is wrong.</p>
  
  <p>Version details:<br>
  - cmake 3.9.0<br>
  - Qt 5.8.0<br>
  - QMake 3.1<br>
  - Mac OS X 10.9.5  </p>