Prospective fix for cmake docs after -fPIC -> -fPIE changes

As a follow-up to qtbase commit 083c9269ed73e8771e1dbe10812696b45b7389f3, cmake
versions older than 2.8.12 require now the use of
Qt5<Module>_EXECUTABLE_COMPILE_FLAGS and the use of cmake's
POSITION_INDEPENDENT_CODE feature is not wanted anymore, as it adds -fPIE to
the build flags, which may override -fPIC and thus cause a build issue when
including qglobal.h.

Change-Id: I4dd6e2ea64f5d8ca8a87f874322bc1b1f8ff5392
Reviewed-by: Stephen Kelly <steveire@gmail.com>

doc/src/development/cmake-manual.qdoc

@@ -96,7 +96,13 @@
     associated. They provide a list of plugins in the
     \c{Qt5}\e{<Module>}\c{_PLUGINS} variable.
 
-    \snippet snippets/cmake/CMakeLists.pro 7
+    \snippet snippets/cmake/CMakeLists.pro 5
+
+    \section2 Using Qt 5 with \c{CMake} older than 2.8.12
+
+    It is also necessary when using an older \c{CMake} to add Qt5<Module>_EXECUTABLE_COMPILE_FLAGS to
+    the CMAKE_CXX_FLAGS so that the -fPIC flags are added to the compile flags if necessary (as
+    is the default with Qt 5).
 
     \section2 Using Qt 5 with \c{CMake} older than 2.8.11
 
@@ -124,24 +130,6 @@
 
     \snippet snippets/cmake/CMakeLists.pro 4
 
-    It is also necessary when using an older \c{CMake} to add Qt5<Module>_EXECUTABLE_COMPILE_FLAGS to
-    the CMAKE_CXX_FLAGS so that the -fPIE flags are added to the compile flags if necessary (as
-    is the default with Qt 5).
-
-    If not using the \c{qt5_use_modules} macro, and if using CMake 2.8.9 or later, the
-    \l{CMake POSITION_INDEPENDENT_CODE Documentation}{POSITION_INDEPENDENT_CODE property} can be set on
-    targets using Qt instead, or it can be set globally for all targets. Note that this is not necessary
-    with CMake 2.8.11:
-
-    \snippet snippets/cmake/CMakeLists.pro 5
-
-    Note that it may be necessary to enable POSITION_INDEPENDENT_CODE globally in order to use try_compile
-    with Qt code, or any wrapper macros around it such as check_cxx_source_compiles etc.
-    As position independent code is a platform-specific and Qt-configuration-specific concept, the
-    Qt5_POSITION_INDEPENDENT_CODE property can be used to check whether it is required.
-
-    \snippet snippets/cmake/CMakeLists.pro 6
-
     \section1 Variable Reference
 
     \section2 Module variables

doc/src/snippets/cmake/CMakeLists.pro

@@ -73,28 +73,8 @@ target_link_libraries(helloworld Qt5::Widgets)
 #! [4]
 
 #! [5]
-find_package(Qt5Core)
-
-add_executable(exe1 ${exe1_SRCS})
-# Set the POSITION_INDEPENDENT_CODE property for the exe1 target...
-set_target_properties(exe1 PROPERTIES POSITION_INDEPENDENT_CODE ON)
-
-# Or set it globally for all targets:
-set(CMAKE_POSITION_INDEPENDENT_CODE ON)
-add_executable(exe2 ${exe2_SRCS})
-
-add_executable(exe3 ${exe3_SRCS})
-#! [5]
-
-#! [6]
-if (Qt5_POSITION_INDEPENDENT_CODE)
-  set(CMAKE_POSITION_INDEPENDENT_CODE ON)
-endif()
-#! [6]
-
-#! [7]
 foreach(plugin ${Qt5Network_PLUGINS})
   get_target_property(_loc ${plugin} LOCATION)
   message("Plugin ${plugin} is at location ${_loc}")
 endforeach()
-#! [7]
+#! [5]