Add "gn check" exception for a downstream builder.

Bug: 1103364
Change-Id: Ic27edc10f6b27c4739d9d2cf027794d919811318
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2288311Reviewed-by: Natalie Chouinard <chouinard@chromium.org>
Commit-Queue: Erik Staab <estaab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#786551}

.gn

@@ -107,6 +107,7 @@ no_check_targets = [
   "//chrome/test:*",  # 2682 errors
   "//chrome:*",  # 7 errors
 
+  "//clank/third_party/gvr_shim:*",  # 1 error
   "//extensions/browser/api/alarms:*",  # 2 errors
   "//extensions/browser/api/app_current_window_internal:*",  # 3 errors
   "//extensions/browser/api/app_runtime:*",  # 3 errors