Build grpcio tools on Windows
diff --git a/tools/run_tests/artifact_targets.py b/tools/run_tests/artifact_targets.py
index 72f4f8d..477bd46 100644
--- a/tools/run_tests/artifact_targets.py
+++ b/tools/run_tests/artifact_targets.py
@@ -151,7 +151,8 @@
     elif self.platform == 'windows':
       return create_jobspec(self.name,
                             ['tools\\run_tests\\build_artifact_python.bat',
-                             self.python_version
+                             self.python_version,
+                             '32' if self.arch == 'x86' else '64'
                             ],
                             shell=True)
     else: