mac: Roll hermetic toolchain to Xcode 8.3.2.

build/mac_toolchain.py

Index: build/mac_toolchain.py
diff --git a/build/mac_toolchain.py b/build/mac_toolchain.py
index 123e5e0d3c0596fe2fb5db214be11477c86ce871..534f9d1982befa883861354b26d1cc7749f8c106 100755
--- a/build/mac_toolchain.py
+++ b/build/mac_toolchain.py
@@ -14,6 +14,7 @@ date:
 """
 
 import os
+import platform
 import plistlib
 import shutil
 import subprocess
@@ -24,10 +25,14 @@ import tempfile
 import urllib2
 
 # This can be changed after running /build/package_mac_toolchain.py.
-MAC_TOOLCHAIN_VERSION = '5B1008'
+MAC_TOOLCHAIN_VERSION = '8E2002'
 MAC_TOOLCHAIN_SUB_REVISION = 3
 MAC_TOOLCHAIN_VERSION = '%s-%s' % (MAC_TOOLCHAIN_VERSION,
                                    MAC_TOOLCHAIN_SUB_REVISION)
+# The toolchain will not be downloaded if the minimum OS version is not met.
+# 16 is the major version number for macOS 10.12.
+MAC_MINIMUM_OS_VERSION = 16
+
 IOS_TOOLCHAIN_VERSION = '8C1002'
 IOS_TOOLCHAIN_SUB_REVISION = 1
 IOS_TOOLCHAIN_VERSION = '%s-%s' % (IOS_TOOLCHAIN_VERSION,
@@ -44,6 +49,13 @@ TOOLCHAIN_BUILD_DIR = os.path.join(BASE_DIR, '%s_files', 'Xcode.app')
 STAMP_FILE = os.path.join(BASE_DIR, '%s_files', 'toolchain_build_revision')
 TOOLCHAIN_URL = 'gs://chrome-mac-sdk/'
 
+
+def PlatformMeetsHermeticXcodeRequirements(target_os):
+  if target_os == 'ios':
+    return True
+  return int(platform.release().split('.')[0]) >= MAC_MINIMUM_OS_VERSION
+
+
 def GetPlatforms():
   default_target_os = ["mac"]
   try:
@@ -232,6 +244,10 @@ def main():
     return 0
 
   for target_os in GetPlatforms():
+    if not PlatformMeetsHermeticXcodeRequirements(target_os):
+      print 'OS version does not support toolchain.'
+      continue
+
     if target_os == 'ios':
       default_version = IOS_TOOLCHAIN_VERSION
       toolchain_filename = 'ios-toolchain-%s.tgz'