CMake: Advocate find_packages(Qt5 COMPONENTS ...) style

This is the style cmake-qt documentation shows nowadays.
For motivation see also

https://blog.kitware.com/cmake-finding-qt5-the-right-way/



Change-Id: I47651c58387b8bf96a2235395f0321e54ad05a88
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

doc/src/development/cmake-manual.qdoc

@@ -56,8 +56,8 @@
     \snippet snippets/cmake/CMakeLists.pro 0
 
     In order for \c{find_package} to be successful, Qt 5 must be found below the CMAKE_PREFIX_PATH,
-    or the Qt5<Module>_DIR must be set in the \c{CMake} cache to the location of the
-    Qt5WidgetsConfig.cmake file. The easiest way to use \c{CMake} is to set the CMAKE_PREFIX_PATH
+    or the \c{Qt5_DIR} must be set in the \c{CMake} cache to the location of the
+    \c{Qt5Config.cmake} file. The easiest way to use \c{CMake} is to set the CMAKE_PREFIX_PATH
     environment variable to the install prefix of Qt 5.
 
     The CMAKE_AUTOMOC setting runs moc automatically when required. For more on this feature see
@@ -105,7 +105,8 @@
     for use. The name of the imported target for each module matches the name of the module with a
     prefix of 'Qt5::', for example Qt5::Widgets. All of the package-specific variables have a
     consistent name with a prefix of the name of the package. For example,
-    \c{find_package}(Qt5Widgets) will make the following variables available if successfully found:
+    \c{find_package(Qt5 COMPONENTS Widgets)} will make the following variables available
+    if successfully found:
 
     \list
     \li Qt5Widgets_VERSION String describing the version of the module.

doc/src/snippets/cmake/CMakeLists.pro

@@ -11,7 +11,7 @@ set(CMAKE_AUTOMOC ON)
 set(CMAKE_AUTOUIC ON)
 
 # Find the QtWidgets library
-find_package(Qt5Widgets CONFIG REQUIRED)
+find_package(Qt5 COMPONENTS Widgets REQUIRED)
 
 # Populate a CMake variable with the sources
 set(helloworld_SRCS
@@ -26,13 +26,13 @@ target_link_libraries(helloworld Qt5::Widgets)
 #! [0]
 
 #! [1]
-find_package(Qt5Core)
+find_package(Qt5 COMPONENTS Core REQUIRED)
 
 get_target_property(QtCore_location Qt5::Core LOCATION)
 #! [1]
 
 #! [2]
-find_package(Qt5Core)
+find_package(Qt5 COMPONENTS Core REQUIRED)
 
 set(CMAKE_CXX_FLAGS_COVERAGE "${CMAKE_CXX_FLAGS_RELEASE} -fprofile-arcs -ftest-coverage")