Change MACOSX_DEPLOYMENT_TARGET to 10.9 (#5406)

* Add kokoro build for python source package

* Use libc++ for xcode 10 (#5303)

The xcode 10 removes the deprecated libstdc++ library. We could set
"MACOSX_DEPLOYMENT_TARGET" to "10.9" to use libc++ instead.

* Add python 3.7 build

* Add build for python 3.7 on linux and windows

* Remove unused source build

* Add comment

* Fix $MACOSX_DEPLOYMENT_TARGET mismatch

* Fix MACOSX_DEPLOYMENT_TARGET mismatch

* Add missing import for sysconfig

* Add missing imports

kokoro/release/python/linux/build_artifacts.sh

@@ -43,3 +43,4 @@ build_artifact_version 2.7
 build_artifact_version 3.4
 build_artifact_version 3.5
 build_artifact_version 3.6
+build_artifact_version 3.7

kokoro/release/python/macos/build_artifacts.sh

@@ -45,3 +45,4 @@ build_artifact_version 2.7
 build_artifact_version 3.4
 build_artifact_version 3.5
 build_artifact_version 3.6
+build_artifact_version 3.7

kokoro/release/python/windows/build_artifacts.bat

@@ -51,3 +51,13 @@ SET PYTHON=C:\python36
 SET PYTHON_VERSION=3.6
 SET PYTHON_ARCH=64
 CALL build_single_artifact.bat
+
+SET PYTHON=C:\python37_32bit
+SET PYTHON_VERSION=3.7
+SET PYTHON_ARCH=32
+CALL build_single_artifact.bat
+
+SET PYTHON=C:\python37
+SET PYTHON_VERSION=3.7
+SET PYTHON_ARCH=64
+CALL build_single_artifact.bat

python/setup.py

 #! /usr/bin/env python
 #
 # See README for usage instructions.
+from distutils import util
 import glob
 import os
+import pkg_resources
+import re
 import subprocess
 import sys
+import sysconfig
 import platform
 
 # We must use setuptools, not distutils, because we need to use the
@@ -185,6 +189,18 @@ if __name__ == '__main__':
     if sys.platform == 'darwin':
       extra_compile_args.append("-Wno-shorten-64-to-32");
 
+    # https://developer.apple.com/documentation/xcode_release_notes/xcode_10_release_notes
+    # C++ projects must now migrate to libc++ and are recommended to set a
+    # deployment target of macOS 10.9 or later, or iOS 7 or later.
+    if sys.platform == 'darwin':
+      mac_target = sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET')
+      if mac_target and (pkg_resources.parse_version(mac_target) <
+                       pkg_resources.parse_version('10.9.0')):
+        os.environ['MACOSX_DEPLOYMENT_TARGET'] = '10.9'
+        os.environ['_PYTHON_HOST_PLATFORM'] = re.sub(
+            r'macosx-[0-9]+\.[0-9]+-(.+)', r'macosx-10.9-\1',
+            util.get_platform())
+
     # https://github.com/Theano/Theano/issues/4926
     if sys.platform == 'win32':
       extra_compile_args.append('-D_hypot=hypot')