fixed ninja setup

Author: Teseo Schneider

setup.py

@@ -46,7 +46,7 @@ def build_extension(self, ext):
 
         if platform.system() == "Windows":
             cmake_args += ['-DCMAKE_LIBRARY_OUTPUT_DIRECTORY_{}={}'.format(cfg.upper(), extdir)]
-            if os.environ.get('CMAKE_GENERATOR') != "NMake Makefiles":
+            if os.environ.get('CMAKE_GENERATOR') != "NMake Makefiles" and os.environ.get('CMAKE_GENERATOR') != "Ninja":
                 if sys.maxsize > 2**32:
                     cmake_args += ['-A', 'x64']
                 # build_args += ['--', '/m']