chore(CI): use cmd:

Author: richardschneider

appveyor.yml

@@ -69,7 +69,7 @@ test_script:
 
 after_test: 
 # Generate coverage report
-    - "%HOMEPATH%\\.nuget\\packages\\OpenCover\\4.6.519\\tools\\OpenCover.Console.exe"
+    - cmd: "%HOMEPATH%\\.nuget\\packages\\OpenCover\\4.6.519\\tools\\OpenCover.Console.exe"
         -register:user -filter:"+[Ipfs*]* -[*Tests]* -[Ipfs.Core]Ipfs.Cryptography.SHA3*" 
         -target:"c:\Program Files\dotnet\dotnet.exe" 
         -targetargs:"test -c Release --no-build --no-restore --framework netcoreapp2.0 test"