dev-manual: document how to provide confs from layer.conf

Add a section on providing global level configuration from the
layer.conf file. Since this file is parsed at an earlier stage in the
parsing process, it's not possible to combine bb.utils.contains and
{DISTRO,MACHINE}_FEATURES to conditionally set some configurations.

This patch documents:

- First that this file can be used for providing such configuration.
- Then demonstrate how to conditionally provide them, using a technique
  that is currently used in meta-virtualization
  (https://git.yoctoproject.org/meta-virtualization/tree/conf/layer.conf#n50).

Fixes [YOCTO #12688].

Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
(From yocto-docs rev: cc3fa1b0e51377f4e03eaa1ca60c2f2ee0cd917e)

Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

0 files changed, 0 insertions, 0 deletions