mac: roll to 10.13 SDK

This change causes the default hermetic SDK to be version 10.13 (aka Xcode 9.3).
This also bumps the minimum build host version to 10.13.2, since that
is the earliest version on which Xcode 9.3 runs.

Bug: 780980
Change-Id: I6da3f7d3a060a22d71d5ee18bb88f51d5aedb0a2
Reviewed-on: https://chromium-review.googlesource.com/c/1394742
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#620032}

build/config/mac/mac_sdk_overrides.gni

@@ -9,14 +9,8 @@ _sdk_min_from_env = getenv("FORCE_MAC_SDK_MIN")
 declare_args() {
   # Minimum supported version of the Mac SDK.
   if (_sdk_min_from_env == "") {
-    mac_sdk_min = "10.12"
+    mac_sdk_min = "10.13"
   } else {
     mac_sdk_min = _sdk_min_from_env
   }
-}
-
+}
\ No newline at end of file
-# Always assert that mac_sdk_min is used on non-macOS platforms to prevent
-# unused args warnings.
-if (!is_mac) {
-  assert(mac_sdk_min == "10.12" || true)
-}

build/mac_toolchain.py

@@ -25,18 +25,12 @@ import sys
 
 # This can be changed after running:
 #    mac_toolchain upload -xcode-path path/to/Xcode.app
-MAC_TOOLCHAIN_VERSION = '8E2002'
+MAC_TOOLCHAIN_VERSION = '9E145'
 
 # 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
-
-# The toolchain will not be downloaded if the maximum OS version is exceeded.
-# 17 is the major version number for macOS 10.13. Xcode 8 does not run on macOS
-# 10.14.
-# TODO(https://crbug.com/780980): Once we build with 10.13 SDK, Xcode 9, we
-# should be able to remove this upper bound.
-MAC_MAXIMUM_OS_VERSION = 17
+# 17 is the major version number for macOS 10.13.
+# 9E145 (Xcode 9.3) only runs on 10.13.2 and newer.
+MAC_MINIMUM_OS_VERSION = 17
 
 MAC_TOOLCHAIN_INSTALLER = 'mac_toolchain'
 
@@ -54,8 +48,7 @@ STAMP_FILE = os.path.join(TOOLCHAIN_ROOT, 'toolchain_build_revision')
 
 def PlatformMeetsHermeticXcodeRequirements():
   major_version = int(platform.release().split('.')[0])
-  return (major_version >= MAC_MINIMUM_OS_VERSION and
-          major_version <= MAC_MAXIMUM_OS_VERSION)
+  return major_version >= MAC_MINIMUM_OS_VERSION
 
 
 def _UseHermeticToolchain():