Build Python 3.9 artifacts for Linux x64 platforms

tools/run_tests/artifacts/artifact_targets.py

@@ -356,6 +356,7 @@ def targets():
         PythonArtifact('manylinux2014', 'x64', 'cp36-cp36m'),
         PythonArtifact('manylinux2014', 'x64', 'cp37-cp37m'),
         PythonArtifact('manylinux2014', 'x64', 'cp38-cp38'),
+        PythonArtifact('manylinux2014', 'x64', 'cp39-cp39'),
         PythonArtifact('manylinux2014', 'x86', 'cp35-cp35m'),
         PythonArtifact('manylinux2014', 'x86', 'cp36-cp36m'),
         PythonArtifact('manylinux2014', 'x86', 'cp37-cp37m'),
@@ -367,6 +368,7 @@ def targets():
         PythonArtifact('manylinux2010', 'x64', 'cp36-cp36m'),
         PythonArtifact('manylinux2010', 'x64', 'cp37-cp37m'),
         PythonArtifact('manylinux2010', 'x64', 'cp38-cp38'),
+        PythonArtifact('manylinux2010', 'x64', 'cp39-cp39'),
         PythonArtifact('manylinux2010', 'x86', 'cp27-cp27m'),
         PythonArtifact('manylinux2010', 'x86', 'cp27-cp27mu'),
         PythonArtifact('manylinux2010', 'x86', 'cp35-cp35m'),