Removed custom QT5_INSTALL_PREFIX variable.

We now use the recommended approach of using CMAKE_PREFIX_PATH
for pointing to Qt5 installations. Passing this variable to
all external projects is a good idea any way (not just for Qt5).

Fixes #478.

CMake/ctkMacroSetupQt.cmake

@@ -32,8 +32,6 @@ macro(ctkMacroSetupQt)
 
   if(CTK_QT_VERSION VERSION_GREATER "4")
     cmake_minimum_required(VERSION 2.8.12)
-    set(QT5_INSTALL_PREFIX "" CACHE PATH "The install location of Qt5")
-    set(CMAKE_PREFIX_PATH ${CMAKE_PREFIX_PATH} ${QT5_INSTALL_PREFIX})
     set(CTK_QT5_COMPONENTS Core Xml XmlPatterns Concurrent Sql Test)
     if(CTK_LIB_Widgets OR CTK_LIB_CommandLineModules/Frontend/QtGui OR CTK_BUILD_ALL OR CTK_BUILD_ALL_LIBRARIES)
       list(APPEND CTK_QT5_COMPONENTS Widgets OpenGL UiTools)
@@ -81,6 +79,5 @@ macro(ctkMacroSetupQt)
 
   mark_as_superbuild(CTK_QT_VERSION)
   mark_as_superbuild(QT_QMAKE_EXECUTABLE) # Qt 4
-  mark_as_superbuild(QT5_INSTALL_PREFIX)  # Qt 5
 
 endmacro()

CMakeExternals/PythonQt.cmake

@@ -35,7 +35,6 @@ if(NOT DEFINED PYTHONQT_INSTALL_DIR)
   if (CTK_QT_VERSION VERSION_GREATER "4")
     list(APPEND ep_PythonQt_args
       -DPythonQt_QT_VERSION:STRING=${CTK_QT_VERSION}
-      -DCMAKE_PREFIX_PATH:STRING=${CMAKE_PREFIX_PATH}
       )
     set(qtlibs Core Gui Widgets Network OpenGL PrintSupport Sql Svg UiTools WebKit WebKitWidgets Xml)
   else()

CMakeLists.txt

@@ -71,6 +71,8 @@ if(NOT CMAKE_CONFIGURATION_TYPES)
   mark_as_superbuild(VARS CMAKE_BUILD_TYPE ALL_PROJECTS)
 endif()
 
+mark_as_superbuild(CMAKE_PREFIX_PATH)
+
 #-----------------------------------------------------------------------------
 # Superbuild Option - Enabled by default
 #