appveyor: enable integration test

Author: iblislin

appveyor.yml

@@ -32,6 +32,7 @@ build_script:
 # Need to convert from shallow to complete for Pkg.clone to work
   - IF EXIST .git\shallow (git fetch --unshallow)
   - C:\projects\julia\bin\julia -e "versioninfo();
+      ENV[\"CONTINUOUS_INTEGRATION\"] = \"1\";
       Pkg.clone(pwd(), \"MXNet\"); Pkg.build(\"MXNet\")"
 
 test_script: