meta-security: add sanity check

Signed-off-by: Armin Kuster <akuster808@gmail.com>

classes/sanity-meta-security.bbclass

@@ -0,0 +1,10 @@
+addhandler security_bbappend_distrocheck
+security_bbappend_distrocheck[eventmask] = "bb.event.SanityCheck"
+python security_bbappend_distrocheck() {
+    skip_check = e.data.getVar('SKIP_META_SECUIRTY_SANITY_CHECK') == "1"
+    if 'security' not in e.data.getVar('DISTRO_FEATURES').split() and not skip_check:
+        bb.warn("You have included the meta-security layer, but \
+'security' has not been enabled in your DISTRO_FEATURES. Some bbappend files \
+and preferred version setting may not take effect. See the meta-security README \
+for details on enabling security support.")
+}