changed watch callback

src/build.ts

@@ -31,14 +31,13 @@ export default async function (
             watch: !watchCallback
                 ? false
                 : {
-                      onRebuild(err, result) {
+                      onRebuild(err, _result) {
+                          let error = null
                           if (err) {
                               console.error(name, err)
-                              let error = (err as BuildFailure).message
-                              watchCallback(metaJson, error)
-                          } else {
-                              console.log('watch build succeeded:', result)
+                              error = (err as BuildFailure).message
                           }
+                          watchCallback(metaJson, error)
                       },
                   },