fixed typo in python script

support/appveyor-build.py

@@ -24,7 +24,7 @@ else:
   if platform == 'x64':
     generator += ' Win64'
   cmake_command.append('-G' + generator)
-  build_command = ['cmake', '--build', '.', '--config', config, '--', '/m:4'],
+  build_command = ['cmake', '--build', '.', '--config', config, '--', '/m:4']
   test_command = ['ctest', '-C', config]
 
 check_call(cmake_command)