Use proper include files in the QtSingleApplication find module.

Look for qtsinglecoreapplication.h when Qt5Widgets module was not found,
and qtsingleapplication.h otherwise. Fixes #9196.

This also removes Qt4 support from the QtSingleApplication find module.

cmake/Modules/FindQtSingleApplication.cmake

@@ -12,28 +12,14 @@
 
 SET(QtSingleApplication_FOUND FALSE)
 
-IF(QT4_FOUND)
+if (Qt5Widgets_FOUND)
-    message(STATUS "Looking for Qt4 single application library")
+    set(_includeFileName qtsingleapplication.h)
-    FIND_PATH(QtSingleApplication_INCLUDE_DIR QtSingleApplication
+else()
-                # standard locations
+    set(_includeFileName qtsinglecoreapplication.h)
-                /usr/include
+endif()
-                /usr/include/QtSolutions
-                # qt4 location except mac's frameworks
-                "${QT_INCLUDE_DIR}/QtSolutions"
-                # mac's frameworks
-                ${FRAMEWORK_INCLUDE_DIR}/QtSolutions
-    )
 
-    SET(QtSingleApplication_NAMES ${QtSingleApplication_NAMES}
-        QtSolutions_SingleApplication-2.6 libQtSolutions_SingleApplication-2.6)
-    FIND_LIBRARY(QtSingleApplication_LIBRARY
-        NAMES ${QtSingleApplication_NAMES}
-        PATHS ${QT_LIBRARY_DIR}
-    )
-ELSEIF(Qt5Core_FOUND)
-    message(STATUS "Looking for Qt5 single application library")
 FOREACH(TOP_INCLUDE_PATH in ${Qt5Core_INCLUDE_DIRS} ${FRAMEWORK_INCLUDE_DIR})
-        FIND_PATH(QtSingleApplication_INCLUDE_DIR QtSingleApplication ${TOP_INCLUDE_PATH}/QtSolutions)
+    FIND_PATH(QtSingleApplication_INCLUDE_DIR ${_includeFileName} ${TOP_INCLUDE_PATH}/QtSolutions)
 
     IF(QtSingleApplication_INCLUDE_DIR)
         BREAK()
@@ -50,7 +36,6 @@ ELSEIF(Qt5Core_FOUND)
     NAMES ${QtSingleApplication_NAMES}
     PATHS ${_QT5_CORELIBRARYPATH}
 )
-ENDIF()
 
 IF (QtSingleApplication_LIBRARY AND QtSingleApplication_INCLUDE_DIR)