Fixes: #57139
Snippets provides the possibility of defining EXTRA_DTC_OVERLAY_FILE and
EXTRA_CONF_FILE in snippets.
Snippets must co-exist with existing infrastructure of
EXTRA_DTC_OVERLAY_FILE and EXTRA_CONF_FILE, and a user specifying a
snippet must be able to specify extra files for adjusting the snippet.
This means that if the following is specified:
`-DSNIPPET=some_snippet -DEXTRA_CONF_FILE=extra.conf`
then `extra.conf` may contain adjustments to the snippet.
Similar to sysbuild. Imagine a sysbuild controlled image uses a default
snippet for building, by ensuring that any extra
`-D<image>_EXTRA_CONF_FILE=extra.conf` arguments takes precedence over
the snippet we allow users to make adjustments if they need.
This commit introduces a snippets scope where snippet scoped variables
can be set with `zephyr_set()` and then `zephyr_get()` will take the
snippet scoped variables into consideration before returning.
Adjust calls to `zephyr_get(EXTRA_DTC_OVERLAY_FILE)` and
`zephyr_get(EXTRA_CONF_FILE)` to use `MERGE` to ensure all scopes are
considered.
Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
ba48dd8763