Add environment variable args to trigger script.

This can allow specifying args such as VK_LOADER_DEBUG.

Bug: chromium:1228274
Change-Id: Idf9298e32a0c6a353891eb8b929a3524d27541b0
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3027539
Reviewed-by: Cody Northrop <cnorthrop@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>

scripts/trigger.py

@@ -45,6 +45,12 @@ def parse_args():
         '--priority',
         help='Task priority. Default is %s. Use judiciously.' % DEFAULT_TASK_PRIORITY,
         default=DEFAULT_TASK_PRIORITY)
+    parser.add_argument(
+        '-e',
+        '--env',
+        action='append',
+        default=[],
+        help='Environment variables. Can be specified multiple times.')
 
     return parser.parse_known_args()
 
@@ -127,6 +133,9 @@ def main():
         swarming_args += ['-service-account', GOLD_SERVICE_ACCOUNT]
         cmd_args += ['luci-auth', 'context', '--']
 
+    for env in args.env:
+        swarming_args += ['--env', env]
+
     cmd_args += swarming_cmd
 
     if unknown: