Fix underlinking problems in shared libraries.

--- a/avogadro/qtplugins/playertool/CMakeLists.txt
+++ b/avogadro/qtplugins/playertool/CMakeLists.txt
@@ -7,3 +7,5 @@
   ""
   playertool.qrc
 )
+
+target_link_libraries(PlayerTool LINK_PRIVATE Qt5OpenGL)
--- a/avogadro/qtplugins/qtaim/CMakeLists.txt
+++ b/avogadro/qtplugins/qtaim/CMakeLists.txt
@@ -34,3 +34,5 @@
 
 target_link_libraries(QTAIMScenePlugin
   LINK_PRIVATE AvogadroRendering ${Qt5Concurrent_LIBRARIES})
+target_link_libraries(QTAIMExtension
+  LINK_PRIVATE ${Qt5Concurrent_LIBRARIES})