[tools] Make sure pinned depot_tools don't auto-update

TBR=sergiyb@chromium.org

Bug: chromium:843917
Change-Id: I7f1c6d7979a76a9573f0673a09444eba26297f05
Reviewed-on: https://chromium-review.googlesource.com/1063971Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53229}

DEPS

@@ -88,6 +88,17 @@ skip_child_includes = [
 ]
 
 hooks = [
+  {
+    # Ensure that the DEPS'd "depot_tools" has its self-update capability
+    # disabled.
+    'name': 'disable_depot_tools_selfupdate',
+    'pattern': '.',
+    'action': [
+        'python',
+        'v8/third_party/depot_tools/update_depot_tools_toggle.py',
+        '--disable',
+    ],
+  },
   {
     # This clobbers when necessary (based on get_landmines.py). It must be the
     # first hook so that other things that get/generate into the output