Autogen: Add release notes for CMAKE_GLOBAL_AUTOGEN/RCC_TARGET

Help/release/dev/autogen_global_target.rst

@@ -0,0 +1,8 @@
+autogen_global_target
+---------------------
+
+* The new variables :variable:`CMAKE_GLOBAL_AUTOGEN_TARGET`,
+  :variable:`CMAKE_GLOBAL_AUTOGEN_TARGET_NAME`,
+  :variable:`CMAKE_GLOBAL_AUTORCC_TARGET` and
+  :variable:`CMAKE_GLOBAL_AUTORCC_TARGET_NAME` control the generation
+  of global ``autogen`` and ``autorcc`` targets.