freertos/local.conf.sample: Avoid build warnings for rauc and security layers

Both layers are currently only targeting the linux flavour so we can
disable the warnings for the flavours where they are not in scope.

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>

flavours/freertos/local.conf.sample

@@ -82,3 +82,7 @@ CONF_VERSION = "2"
 # *and* the project you are building has a public sstate cache, you may choose to uncomment
 # this line and use the sstate cache published by Oniro Project.
 # SSTATE_MIRRORS = "file://.* https://cache.ostc-eu.org/bitbake/sstate-cache/PATH;downloadfilename=PATH \n"
+
+# Avoid warnings for included layers
+SKIP_META_SECURITY_SANITY_CHECK = "1"
+SKIP_META_RAUC_FEATURE_CHECK = "1"