add sync-rootfs script

.devcontainer/toolchain/scripts/sync-rootfs.sh

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+
+set -o errexit
+set -o pipefail
+set -o nounset
+# set -o xtrace
+
+rsync -crlpgoD -i \
+  --exclude=/etc/ssh/** \
+  --exclude=/etc/hostname \
+  --exclude=/etc/group \
+  --exclude=/etc/passwd \
+  --exclude=/etc/shadow \
+  --exclude=/etc/fstab \
+  --exclude=THIS_IS_NOT_YOUR_ROOT_FILESYSTEM \
+  /buildroot/output/target/ \
+  /rootfs/