title: This application failed to start because it could not find or load the Qt platform plugin "xcb"
body: <p>this <a href="https://stackoverflow.com/questions/29405689/qt-5-4-1-this-application-failed-to-start-because-it-could-not-find-or-load-th">exist answer</a> can not fix my question</p>
  
  <p>In qt <a href="https://github.com/qtproject/qtbase/tree/5.5/examples/widgets/desktop/systray" rel="nofollow noreferrer">official example</a>, I use following CMakeLists.txt</p>
  
  <pre><code>SET(CMAKE_PREFIX_PATH /media/roroco/disk750/Downloads/qtbase)
  set(CMAKE_INCLUDE_CURRENT_DIR ON)
  set(CMAKE_AUTOMOC ON)
  set(CMAKE_AUTORCC ON)
  find_package(Qt5Widgets)
  find_library(xcb NAMES qxcb PATHS /media/roroco/disk750/Downloads/qtbase/plugins/platforms)
  add_executable(systray main.cpp window.cpp systray.qrc)
  target_link_libraries(systray Qt5::Widgets ${xcb})
  </code></pre>
  
  <p>and I get </p>
  
  <pre><code>This application failed to start because it could not find or load the Qt platform plugin "xcb".
  </code></pre>
  
  <p>How to add "xcb" plugin to cmake?</p>
  
  <p><strong>update</strong></p>
  
  <p>I'm sure <code>find_library(xcb</code> find the lib "/media/roroco/disk750/Downloads/qtbase/plugins/platforms/libqxcb.so".</p>