Added a comment

setup.py

@@ -147,6 +147,7 @@ class CMakeBuild(build_ext):
             cmake_args += ['-DCMAKE_LIBRARY_OUTPUT_DIRECTORY_{}={}'.format(cfg.upper(), extdir)]
             if sys.maxsize > 2**32:
                 cmake_args += ['-A', 'x64']
+            # Do a parallel build
             build_args += ['--', '/m'] 
         else:
             cmake_args += ['-DCMAKE_BUILD_TYPE=' + cfg]