sync call to write file, avoid vif loading error

fix https://github.com/chrislusf/seaweedfs/issues/2633

weed/util/file_util.go

@@ -95,3 +95,20 @@ func FileNameBase(filename string) string {
 	}
 	return filename[:lastDotIndex]
 }
+
+// Copied from os.WriteFile(), adding file sync.
+// see https://github.com/golang/go/issues/20599
+func WriteFile(name string, data []byte, perm os.FileMode) error {
+	f, err := os.OpenFile(name, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, perm)
+	if err != nil {
+		return err
+	}
+	_, err = f.Write(data)
+	if err1 := f.Sync(); err1 != nil && err == nil {
+		err = err1
+	}
+	if err1 := f.Close(); err1 != nil && err == nil {
+		err = err1
+	}
+	return err
+}