Help: Clarify version adding add_custom_{command,target} OUTPUT genex support

Update the documentation added by commit c257c25419
(add_custom_{command,target}: Add genex support to OUTPUT and
BYPRODUCTS, 2020-10-19) to use sphinx markup instead of prose to specify
the version in which the feature was added.

Help/command/add_custom_command.rst

@@ -79,7 +79,8 @@ The options are:
   The :ref:`Makefile Generators` will remove ``BYPRODUCTS`` and other
   :prop_sf:`GENERATED` files during ``make clean``.
 
-  Since CMake 3.20, arguments to ``BYPRODUCTS`` may use
+  .. versionadded:: 3.20
+    Arguments to ``BYPRODUCTS`` may use
     :manual:`generator expressions <cmake-generator-expressions(7)>`.
 
 ``COMMAND``
@@ -229,7 +230,8 @@ The options are:
   as a file on disk it should be marked with the :prop_sf:`SYMBOLIC`
   source file property.
 
-  Since CMake 3.20, arguments to ``OUTPUT`` may use
+  .. versionadded:: 3.20
+    Arguments to ``OUTPUT`` may use
     :manual:`generator expressions <cmake-generator-expressions(7)>`.
 
 ``USES_TERMINAL``
@@ -291,10 +293,11 @@ adds a custom command to run ``someTool`` to generate ``out.c`` and then
 compile the generated source as part of a library.  The generation rule
 will re-run whenever ``in.txt`` changes.
 
-Since CMake 3.20, one may use generator expressions to specify
+.. versionadded:: 3.20
-per-configuration outputs.  For example, the code:
+  One may use generator expressions to specify per-configuration outputs.
+  For example, the code:
 
-.. code-block:: cmake
+  .. code-block:: cmake
 
     add_custom_command(
       OUTPUT "out-$<CONFIG>.c"
@@ -305,9 +308,9 @@ per-configuration outputs.  For example, the code:
       VERBATIM)
     add_library(myLib "out-$<CONFIG>.c")
 
-adds a custom command to run ``someTool`` to generate ``out-<config>.c``,
+  adds a custom command to run ``someTool`` to generate ``out-<config>.c``,
-where ``<config>`` is the build configuration, and then compile the generated
+  where ``<config>`` is the build configuration, and then compile the generated
-source as part of a library.
+  source as part of a library.
 
 Build Events
 ^^^^^^^^^^^^
@@ -377,10 +380,11 @@ For example, the code:
 will run ``someHasher`` to produce a ``.hash`` file next to the executable
 after linking.
 
-Since CMake 3.20, one may use generator expressions to specify
+.. versionadded:: 3.20
-per-configuration byproducts.  For example, the code:
+  One may use generator expressions to specify per-configuration byproducts.
+  For example, the code:
 
-.. code-block:: cmake
+  .. code-block:: cmake
 
     add_library(myPlugin MODULE myPlugin.c)
     add_custom_command(
@@ -391,6 +395,6 @@ per-configuration byproducts.  For example, the code:
       VERBATIM)
     add_executable(myExe myExe.c "myPlugin-hash-$<CONFIG>.c")
 
-will run ``someHasher`` after linking ``myPlugin``, e.g. to produce a ``.c``
+  will run ``someHasher`` after linking ``myPlugin``, e.g. to produce a ``.c``
-file containing code to check the hash of ``myPlugin`` that the ``myExe``
+  file containing code to check the hash of ``myPlugin`` that the ``myExe``
-executable can use to verify it before loading.
+  executable can use to verify it before loading.

Help/command/add_custom_target.rst

@@ -54,7 +54,8 @@ The options are:
   The :ref:`Makefile Generators` will remove ``BYPRODUCTS`` and other
   :prop_sf:`GENERATED` files during ``make clean``.
 
-  Since CMake 3.20, arguments to ``BYPRODUCTS`` may use
+  .. versionadded:: 3.20
+    Arguments to ``BYPRODUCTS`` may use
     :manual:`generator expressions <cmake-generator-expressions(7)>`.
 
 ``COMMAND``