I was having difficulty building Chromium's component build per  Issue 620127  and, per advice, manually installed the 10.10 SDK into Xcode. (I had previously been running an older version, and also upgraded it to 7.3.1 at the same time.)

After taking the latest macOS security updates I was no longer able to build; "gn gen out/Release" complained that xcrun, and therefore find_sdk.py, couldn't run successfully while that 10.10 SDK was installed:

**********
kbr-macbookpro4:src kbr$ gn gen out/Release
ERROR at //build/config/mac/mac_sdk.gni:54:5: Script returned non-zero exit code.
    exec_script("//build/mac/find_sdk.py", find_sdk_args, "list lines")
    ^----------
Current dir: /Users/kbr/src/chrome/src/out/Release/
Command: python -- /Users/kbr/src/chrome/src/build/mac/find_sdk.py --print_sdk_path 10.10
Returned 1.
stderr:

2016-09-24 16:32:08.772 xcodebuild[70979:341740] [MT] DVTSDK: Skipped SDK /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk; its version (10.10) is below required minimum (10.11) for the macosx platform.
xcodebuild: error: SDK "macosx10.10" cannot be located.
2016-09-24 16:32:09.192 xcodebuild[70984:341764] [MT] DVTSDK: Skipped SDK /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk; its version (10.10) is below required minimum (10.11) for the macosx platform.
xcodebuild: error: SDK "macosx10.10" cannot be located.
xcrun: error: unable to lookup item 'Path' in SDK 'macosx10.10'
Traceback (most recent call last):
  File "/Users/kbr/src/chrome/src/build/mac/find_sdk.py", line 90, in <module>
    print main()
  File "/Users/kbr/src/chrome/src/build/mac/find_sdk.py", line 82, in main
    ['xcrun', '-sdk', 'macosx' + best_sdk, '--show-sdk-path']).strip()
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 573, in check_output
    raise CalledProcessError(retcode, cmd, output=output)
subprocess.CalledProcessError: Command '['xcrun', '-sdk', 'macosx10.10', '--show-sdk-path']' returned non-zero exit status 1

See //build/toolchain/mac/BUILD.gn:14:1: whence it was imported.
import("//build/config/mac/mac_sdk.gni")
^--------------------------------------
See //BUILD.gn:71:1: which caused the file to be included.
group("gn_all") {
^----------------
**********

Removing the 10.10 SDK from Xcode prevented the component build from working; the same problem described in  Issue 620127  was still happening.

In the hope that upgrading to Xcode 8 might help I did so and now can not compile. I've disabled goma. Here is the error:

ninja: Entering directory `out/Release'
[726/26505] LINK obj/chrome/chrome_helper_app_executable/Chromium Helper
FAILED: obj/chrome/chrome_helper_app_executable/Chromium Helper 
TOOL_VERSION=1471414135 ../../build/toolchain/mac/linker_driver.py ../../third_party/llvm-build/Release+Asserts/bin/clang++  -stdlib=libc++ -arch x86_64 -Wl,-dead_strip -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk -mmacosx-version-min=10.7 -Wl,-ObjC -Wl,-pie -o "obj/chrome/chrome_helper_app_executable/Chromium Helper" -Wl,-filelist,"obj/chrome/chrome_helper_app_executable/Chromium Helper.rsp"  
ld: unexpected token: !tapi-tbd-v2 file '/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk/usr/lib/libc++.tbd' for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Traceback (most recent call last):
  File "../../build/toolchain/mac/linker_driver.py", line 222, in <module>
    Main(sys.argv)
  File "../../build/toolchain/mac/linker_driver.py", line 72, in Main
    subprocess.check_call(compiler_driver_args)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 540, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['../../third_party/llvm-build/Release+Asserts/bin/clang++', '-stdlib=libc++', '-arch', 'x86_64', '-Wl,-dead_strip', '-isysroot', '/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk', '-mmacosx-version-min=10.7', '-Wl,-ObjC', '-Wl,-pie', '-o', 'obj/chrome/chrome_helper_app_executable/Chromium Helper', '-Wl,-filelist,obj/chrome/chrome_helper_app_executable/Chromium Helper.rsp']' returned non-zero exit status 1
[735/26505] ACTION //chrome/app/nibs:chrome_xibs_compile_ibtool(//build/toolchain/mac:clang_x64)
ninja: build stopped: subcommand failed.

My source tree is current as of yesterday (Friday September 23).

Could anyone help? Is Xcode 8 supported for Chromium builds on 10.11.6? This is on a corp laptop. Thanks.