Make sure variables are exported for run-parts in 999-extras.binary; and drop the unnecessary sourcing of functions.

live-build/ubuntu-cpc/hooks/999-extras.binary

@@ -8,12 +8,9 @@ if [ ! -d ${my_dir}/extra ]; then
     exit 0
 fi
 
-IMAGE_STR="# CLOUD_IMG: This file was created/modified by the Cloud Image build process"
-CLOUD_IMG_STR="$IMAGE_STR"
-FS_LABEL="cloudimg-rootfs"
-
-# Export the common functions to the extras
-. config/functions
+export IMAGE_STR="# CLOUD_IMG: This file was created/modified by the Cloud Image build process"
+export CLOUD_IMG_STR="$IMAGE_STR"
+export FS_LABEL="cloudimg-rootfs"
 
 # Cleaner execution
 /bin/run-parts --regex ".*\.binary" "${extra_d}"