linux-yocto%.bbappend: Add audit.cfg

Add audit.cfg configuration fragment. By default it is not appended
to SRC_URI. It allows enabling the audit kernel subsystem which may
help to debug appraisal issues. Boot with "integrity_audit=1" to
capture a more complete set of events in /var/log/audit/.

Previously the same configuration fragment was provided by layer
meta-security-framework but it is no longer maintained therefore it
makes sense to have audit.cfg in layer meta-integrity.

Signed-off-by: Leon Anavi <leon.anavi@konsulko.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>

meta-integrity/recipes-kernel/linux/linux-yocto%.bbappend

@@ -1 +1,3 @@
+FILESEXTRAPATHS:prepend := "${THISDIR}/linux:"
+
 require ${@bb.utils.contains_any('DISTRO_FEATURES', 'integrity ', 'linux_ima.inc', '', d)}

meta-integrity/recipes-kernel/linux/linux/audit.cfg

@@ -0,0 +1,2 @@
+CONFIG_AUDIT=y
+CONFIG_AUDITSYSCALL=y