ref-manual: classes.rst: improvements to cmake class documentation

- Fix quoting for path to cmake modules
- Document OECMAKE_GENERATOR variable
- Style simplifications

(From yocto-docs rev: ecdc1775e27717ec87442575f65b1f24ca2b0348)

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Reviewed-by: Quentin Schulz <foss+yocto@0leil.net>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

2 files changed, 24 insertions, 11 deletions

diff --git a/documentation/ref-manual/classes.rst b/documentation/ref-manual/classes.rst
index 4fdc4c583e..b9b49981e1 100644
--- a/documentation/ref-manual/classes.rst
+++ b/documentation/ref-manual/classes.rst
@@ -346,17 +346,20 @@ in order to make them relocatable.
 ``cmake``
 =========
 
-The ref:`ref-classes-cmake` class allows for recipes that need to build software using
-the `CMake <https://cmake.org/overview/>`__ build system. You can use
-the :term:`EXTRA_OECMAKE` variable to specify
-additional configuration options to be passed using the ``cmake``
-command line.
-
-On the occasion that you would be installing custom CMake toolchain
-files supplied by the application being built, you should install them
-to the preferred CMake Module directory: ``${D}${datadir}/cmake/``
-Modules during
-:ref:`ref-tasks-install`.
+The :ref:`ref-classes-cmake` class allows recipes to build software using the
+`CMake <https://cmake.org/overview/>`__ build system. You can use the
+:term:`EXTRA_OECMAKE` variable to specify additional configuration options to
+pass to the ``cmake`` command line.
+
+By default, the :ref:`ref-classes-cmake` class uses
+`Ninja <https://ninja-build.org/>`__ instead of GNU make for building, which
+offers better build performance. If a recipe is broken with Ninja, then the
+recipe can set the :term:`OECMAKE_GENERATOR` variable to ``Unix Makefiles`` to
+use GNU make instead.
+
+If you need to install custom CMake toolchain files supplied by the application
+being built, you should install them (during :ref:`ref-tasks-install`) to the
+preferred CMake Module directory: ``${D}${datadir}/cmake/modules/``.
 
 .. _ref-classes-cml1:
 
diff --git a/documentation/ref-manual/variables.rst b/documentation/ref-manual/variables.rst
index 62176f7ee8..c204f49aac 100644
--- a/documentation/ref-manual/variables.rst
+++ b/documentation/ref-manual/variables.rst
@@ -5399,6 +5399,16 @@ system and gives an overview of their function and contents.
       :term:`Source Directory` for details on how this class
       applies these additional sed command arguments.
 
+   :term:`OECMAKE_GENERATOR`
+      A variable for the :ref:`ref-classes-cmake` class, allowing to choose
+      which back-end will be generated by CMake to build an application.
+
+      By default, this variable is set to ``Ninja``, which is faster than GNU
+      make, but if building is broken with Ninja, a recipe can use this
+      variable to use GNU make instead::
+
+         OECMAKE_GENERATOR = "Unix Makefiles"
+
    :term:`OE_IMPORTS`
       An internal variable used to tell the OpenEmbedded build system what
       Python modules to import for every Python function run by the system.