roll the mac toolchain to use binaries from Xcode 10.12.1.

This has the main effect of rolling the ld version to pick up a fix to
deterministic builds. This has the side effect of including the 10.14 SDK so
that it's easier to roll the SDK that Chrome uses to build.

Bug: 330262, 943106
Change-Id: I747c2d1d0f3a588548df6b92fdac27beccf45d71
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1711044Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#679322}

build/mac_toolchain.py

@@ -38,10 +38,10 @@ import sys
 # xcode_binaries, see InstallXcodeBinaries. https://crbug.com/984746
 MAC_TOOLCHAIN_VERSION = '9E501'
 
-# This contains binaries from Xcode 9.3.1, along with the 10.13 SDK.
-# To build this package, see comments in build/xcode_binaries.yaml
+# This contains binaries from Xcode 10.12.1, along with the 10.13 and 10.14
+# SDKs. To build this package, see comments in build/xcode_binaries.yaml
 MAC_BINARIES_LABEL = 'infra_internal/ios/xcode/xcode_binaries/mac-amd64'
-MAC_BINARIES_TAG = 'oXeIQqw4E0pXIStoixHwKg_1TJZTJGhfhmn2fq8LPOAC'
+MAC_BINARIES_TAG = '4SpEve_8bN_DmTH0QdxMQoCTsrAe5QK04uoMEnNHAvQC'
 
 # The toolchain will not be downloaded if the minimum OS version is not met.
 # 17 is the major version number for macOS 10.13.