Change passive voice to active voice and fix a grammar error

As per coq#12411 (comment)

doc/sphinx/practical-tools/utilities.rst

@@ -141,18 +141,19 @@ Including the generated makefile with an include directive is
 discouraged, since the contents of this file, including variable names and
 status of rules, may change in the future.
 
-An optional file ``CoqMakefile.local`` can be provided by the user in order to
-extend ``CoqMakefile``. In particular one can declare custom actions to be
-performed before or after the build process. Similarly one can customize the
-install target or even provide new targets. Extension points are documented in
-paragraph :ref:`coqmakefilelocal`. If the user needs to access variables
-defined in the ``Makefile`` in a way not covered by `secondary expansion
+Use the optional file ``CoqMakefile.local`` to extend
+``CoqMakefile``. In particular, you can declare custom actions to be
+performed before or after the build process. Similarly you can
+customize the install target or even provide new targets. See
+:ref:`coqmakefilelocal` for extension-point documentation. To access
+variables defined in the ``Makefile`` in a way not covered by
+`secondary expansion
 <https://www.gnu.org/software/make/manual/html_node/Secondary-Expansion.html>`_,
-for example to add new dependencies to compiled outputs, the optional file
-``CoqMakefile.local-late`` can be used.  A non-exhaustive list is documented in
-paragraph :ref:`coqmakefilelocallate`.
+for example to add new dependencies to compiled outputs, use the
+optional file ``CoqMakefile.local-late``.  See
+:ref:`coqmakefilelocallate` for a non-exhaustive list.
 
-The extensions of the files listed in ``_CoqProject`` is used in order to
+The extensions of the files listed in ``_CoqProject`` are used in order to
 decide how to build them. In particular: