Add hook to fetch reclient config files

(Initially uploaded here https://crrev.com/c/5726652)

This logic was copied from the login in chromium/src at https://chromium-review.googlesource.com/c/chromium/src/+/4666325 as that is the current version of buildtools that libyuv uses
This is needed to be able to remove the old path of downloading remote exec configs on ci builders

Test: CQ tryjobs

No-Try: true
Bug: b/292501270
Change-Id: Idea22e9a499e57d86f1e1e8ed9c0ca346aa162b6
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/6055341
Reviewed-by: Mirko Bonadei <mbonadei@chromium.org>
Reviewed-by: Christoffer Dewerin <jansson@chromium.org>
Commit-Queue: Mirko Bonadei <mbonadei@chromium.org>

DEPS

@@ -12,6 +12,13 @@ vars = {
   'ninja_version': 'version:2@1.11.1.chromium.6',
   # reclient CIPD package version
   'reclient_version': 're_client_version:0.110.0.43ec6b1-gomaip',
+  # Fetch configuration files required for the 'use_remoteexec' gn arg
+  'download_remoteexec_cfg': False,
+  # RBE instance to use for running remote builds
+  'rbe_instance': Str('projects/rbe-webrtc-developer/instances/default_instance'),
+  # RBE project to download rewrapper config files for. Only needed if
+  # different from the project used in 'rbe_instance'
+  'rewrapper_cfg_project': Str(''),
 
   # Keep the Chromium default of generating location tags.
   'generate_location_tags': True,
@@ -2561,6 +2568,22 @@ hooks = [
       'src/testing/location_tags.json',
     ],
   },
+  # Download remote exec cfg files
+  {
+    'name': 'fetch_reclient_cfgs',
+    'pattern': '.',
+    'condition': 'download_remoteexec_cfg',
+    'action': ['python3',
+               'src/buildtools/reclient_cfgs/fetch_reclient_cfgs.py',
+               '--rbe_instance',
+               Var('rbe_instance'),
+               '--reproxy_cfg_template',
+               'reproxy.cfg.template',
+               '--rewrapper_cfg_project',
+               Var('rewrapper_cfg_project'),
+               '--quiet',
+               ],
+  },
 ]
 
 recursedeps = []