skip building branches with a PR open

prevent building both branch and pr/merge when an active PR is open

appveyor.yml

@@ -1,6 +1,9 @@
 version: 1.0.0.{build}
 image: Visual Studio 2017
 
+# prevent the double build when a branch has an active PR
+skip_branch_with_pr: true
+
 init:
   - ps: iex ((new-object net.webclient).DownloadString('https://gist.githubusercontent.com/PureKrome/0f79e25693d574807939/raw/8cf3160c9516ef1f4effc825c0a44acc918a0b5a/appveyor-build-info.ps'))