apparmor: mount more up-to-date apparmor features in the chroot.

(cherry picked from commit a14a31b751)

live-build/auto/build

@@ -121,6 +121,8 @@ preinstall_snaps() {
 	mount --rbind /dev chroot/dev
 	mount --rbind /sys chroot/sys
 	mount --bind /proc chroot/proc
+	# Provide more up to date apparmor features, matching target kernel
+	mount -o bind /usr/share/livecd-rootfs/live-build/apparmor/generic chroot/sys/kernel/security/apparmor/features
 
 	snap_validate_seed chroot
 

live-build/functions

@@ -105,6 +105,8 @@ setup_mountpoint() {
     mount proc-live -t proc "$mountpoint/proc"
     mount sysfs-live -t sysfs "$mountpoint/sys"
     mount securityfs -t securityfs "$mountpoint/sys/kernel/security"
+    # Provide more up to date apparmor features, matching target kernel
+    mount -o bind /usr/share/livecd-rootfs/live-build/apparmor/generic "$mountpoint/sys/kernel/security/apparmor/features/"
     mount -t tmpfs none "$mountpoint/tmp"
     mount -t tmpfs none "$mountpoint/var/lib/apt"
     mount -t tmpfs none "$mountpoint/var/cache/apt"