docs: replace `FOO by :term:FOO` where possible

If a variable has a glossary entry and some rST files write about those
variables, it's better to point to the glossary entry instead of just
highlighting it by surrounding it with two tick quotes.

This was automated by the following python script:
"""
import re
from pathlib import Path

with open('objects.inv.txt', 'r') as f:
    objects = f.readlines()

with open('bitbake-objects.inv.txt', 'r') as f:
    objects = objects + f.readlines()

re_term = re.compile(r'variables.html#term-([A-Z_0-9]*)')
terms = []

for obj in objects:
    match = re_term.search(obj)
    if match and match.group(1):
        terms.append(match.group(1))

for rst in Path('.').rglob('*.rst'):
    with open(rst, 'r') as f:
        content = "".joing(f.readlines())
    for term in terms:
        content = re.sub(r'``({})``(?!.*\s*[~-]+)'.format(term), r':term:`\1`', content)

    with open(rst, 'w') as f:
        f.write(content)
"""

(From yocto-docs rev: ba49d9babfcb84bc5c26a68c8c3880a1d9c236d3)

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

documentation/ref-manual/features.rst

@@ -10,10 +10,10 @@ can select, and a reference on feature backfilling.
 
 Features provide a mechanism for working out which packages should be
 included in the generated images. Distributions can select which
-features they want to support through the ``DISTRO_FEATURES`` variable,
+features they want to support through the :term:`DISTRO_FEATURES` variable,
 which is set or appended to in a distribution's configuration file such
 as ``poky.conf``, ``poky-tiny.conf``, ``poky-lsb.conf`` and so forth.
-Machine features are set in the ``MACHINE_FEATURES`` variable, which is
+Machine features are set in the :term:`MACHINE_FEATURES` variable, which is
 set in the machine configuration file and specifies the hardware
 features for a given machine.
 
@@ -267,7 +267,7 @@ these valid features is as follows:
 -  *ssh-server-openssh:* Installs the OpenSSH SSH server, which is more
    full-featured than Dropbear. Note that if both the OpenSSH SSH server
    and the Dropbear minimal SSH server are present in
-   ``IMAGE_FEATURES``, then OpenSSH will take precedence and Dropbear
+   :term:`IMAGE_FEATURES`, then OpenSSH will take precedence and Dropbear
    will not be installed.
 
 -  *tools-debug:* Installs debugging tools such as ``strace`` and
@@ -323,27 +323,27 @@ Here are two examples to help illustrate feature backfilling:
 -  *The "pulseaudio" distro feature option*: Previously, PulseAudio
    support was enabled within the Qt and GStreamer frameworks. Because
    of this, the feature is backfilled and thus enabled for all distros
-   through the ``DISTRO_FEATURES_BACKFILL`` variable in the
+   through the :term:`DISTRO_FEATURES_BACKFILL` variable in the
    ``meta/conf/bitbake.conf`` file. However, your distro needs to
    disable the feature. You can disable the feature without affecting
    other existing distro configurations that need PulseAudio support by
-   adding "pulseaudio" to ``DISTRO_FEATURES_BACKFILL_CONSIDERED`` in
+   adding "pulseaudio" to :term:`DISTRO_FEATURES_BACKFILL_CONSIDERED` in
    your distro's ``.conf`` file. Adding the feature to this variable
-   when it also exists in the ``DISTRO_FEATURES_BACKFILL`` variable
+   when it also exists in the :term:`DISTRO_FEATURES_BACKFILL` variable
    prevents the build system from adding the feature to your
-   configuration's ``DISTRO_FEATURES``, effectively disabling the
+   configuration's :term:`DISTRO_FEATURES`, effectively disabling the
    feature for that particular distro.
 
 -  *The "rtc" machine feature option*: Previously, real time clock (RTC)
    support was enabled for all target devices. Because of this, the
    feature is backfilled and thus enabled for all machines through the
-   ``MACHINE_FEATURES_BACKFILL`` variable in the
+   :term:`MACHINE_FEATURES_BACKFILL` variable in the
    ``meta/conf/bitbake.conf`` file. However, your target device does not
    have this capability. You can disable RTC support for your device
    without affecting other machines that need RTC support by adding the
-   feature to your machine's ``MACHINE_FEATURES_BACKFILL_CONSIDERED``
+   feature to your machine's :term:`MACHINE_FEATURES_BACKFILL_CONSIDERED`
    list in the machine's ``.conf`` file. Adding the feature to this
-   variable when it also exists in the ``MACHINE_FEATURES_BACKFILL``
+   variable when it also exists in the :term:`MACHINE_FEATURES_BACKFILL`
    variable prevents the build system from adding the feature to your
-   configuration's ``MACHINE_FEATURES``, effectively disabling RTC
+   configuration's :term:`MACHINE_FEATURES`, effectively disabling RTC
    support for that particular machine.