Fix appveyor build spec

appveyor.yml

@@ -2,8 +2,8 @@ version: 1.0.{build}
 branches:
   only:
   - master
-  - ^v\\d+(?:.\\d+)?$
-  - '[\b_]validate\b'
+  - /^v\\d+(?:.\\d+)?$/
+  - /[\b_]validate\b/
 skip_tags: true
 nuget:
   disable_publish_on_pr: true