live-build: move snap seed validation into preinstall_snaps (thanks to rcj)

live-build/auto/build

@@ -88,6 +88,11 @@ preinstall_snaps() {
 		snap_preseed chroot "${snap}"
 	done
 	lb chroot_resolv remove
+
+        # Do basic validation of generated snapd seed.yaml.
+        if [ -e chroot/var/lib/snapd/seed/seed.yaml ]; then
+            snap debug validate-seed chroot/var/lib/snapd/seed/seed.yaml
+        fi
 }
 
 rm -f binary.success
@@ -529,11 +534,6 @@ if [ -z "$PASSES" ] && [ -e "$PREFIX.manifest" ]; then
 	./config/snap-seed-parse "chroot/" "$PREFIX.manifest"
 fi
 
-# Do basic validation of generated snapd seed.yaml.
-if [ -e chroot/var/lib/snapd/seed/seed.yaml ]; then
-    snap debug validate-seed chroot/var/lib/snapd/seed/seed.yaml
-fi
-
 # ubuntu-core splits kernel stuff into a "device" tarball so
 # at this point we reset it to "none" as all the work to extract it was done already
 # in a binary hook