better mikdim-script

docker/builder/mikdim-script

@@ -188,7 +188,7 @@ if [ -z "$working_branch" ]; then
     working_branch="$CI_MERGE_REQUEST_TARGET_BRANCH_NAME"
 fi
 
-if [ -z "$working_branch" -a -z "$test_mode" ]; then
+if [ -z "$working_branch" -a -z "$test_mode" -a -z "$install_only" ]; then
     msg --warning "Warning: skipping build on non-branches"
     exit 0
 fi