UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/602.1.50 (KHTML, like Gecko) Version/10.0 Safari/602.1.50

Steps to reproduce the problem:
1. I have checkout a release branch of webrtc (say 51) which compiles perfectly on my machine, and on which my product depends.
2. when i run a depot_tool command , depot_tools autoupdates
3a. I can't compile anymore since now depot_tools require iOS sdk 11, which only comes with xcode 8, on OSX sierra ...
3b I can't compile anymore since depot_tools now requires MSVC 2015
4. I can't find which version of depot_tool I should use, and there are high chances that it would auto_update as well.

What is the expected behavior?
it would be nice, at least, to have:
- depot_tools tagged synchronously with release_banches
- a way to disable depot_tool auto update

What went wrong?
see 3a, 3b, and 4 above.

Did this work before? No 

Chrome version: many  Channel: stable
OS Version: OS X 10.11.6
Flash Version: