chroot_prep: warn if running archives helper for bootstrap stage

to protect against simple mistake of using 'all' instead of
'all-except-archives' when manually executing scripts (e.g. during
development) at the bootstrap stage level. (the bootstrap stage does not
and should not use the archives helper).

Gbp-Dch: Ignore

scripts/build/chroot_prep

@@ -94,6 +94,10 @@ if In_list "archives" ${HELPERS} && [ -z "${ARCHIVES_PASS}" ]; then
 	exit 1
 fi
 
+if In_list "archives" ${HELPERS} && [ ! -e .build/bootstrap ]; then
+	Echo_warning "The 'archives' helper is selected, but the bootstrap stage has not completed."
+fi
+
 if [ "${_ACTION}" = "remove" ]; then
 	HELPERS_REVERSED=""
 	for HELPER in $HELPERS; do