Merge pull request #1457 from jedevc/add-hosts-length-check

build: don't set add-hosts option if empty

build/build.go

@@ -624,7 +624,9 @@ func toSolveOpt(ctx context.Context, node builder.Node, multiDriver bool, opt Op
 	if err != nil {
 		return nil, nil, err
 	}
-	so.FrontendAttrs["add-hosts"] = extraHosts
+	if len(extraHosts) > 0 {
+		so.FrontendAttrs["add-hosts"] = extraHosts
+	}
 
 	// setup shm size
 	if opt.ShmSize.Value() > 0 {