Merge branch 'externalproject_docs' into release-3.14

Merge-request: !2978

Help/release/3.14.rst

@@ -172,7 +172,7 @@ Modules
 * The :module:`ExternalProject` module :command:`ExternalProject_Add` command
   gained ``LOG_PATCH`` to optionally log the patch step.
 
-* The :module:`ExternalProject` module's ``ExternalProject_Add`` command
+* The :module:`ExternalProject` module :command:`ExternalProject_Add` command
   learned to apply ``SOURCE_SUBDIR`` when ``BUILD_IN_SOURCE`` is also used.
   The ``BUILD_COMMAND`` is run in the given ``SOURCE_SUBDIR`` of the
   ``SOURCE_DIR``.

Modules/ExternalProject.cmake

@@ -550,7 +550,8 @@ External Project Definition
       When enabled, the output of the test step is logged to files.
 
     ``LOG_MERGED_STDOUTERR <bool>``
-      When enabled, the output the step is not split by stdout and stderr.
+      When enabled, stdout and stderr will be merged for any step whose
+      output is being logged to files.
 
     ``LOG_OUTPUT_ON_FAILURE <bool>``
       This option only has an effect if at least one of the other ``LOG_<step>``