[infra] Add gc_stats variant to Linux64 debug bot

No-try: true
Bug: v8:7760
Change-Id: I2a4e91b58de4387a4bfa5b79681db25880af8954
Reviewed-on: https://chromium-review.googlesource.com/1068643
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53394}

infra/testing/builders.pyl

@@ -397,6 +397,7 @@
   },
   'V8 Linux64 - debug': {
     'tests': [
+      {'name': 'v8testing', 'variant': 'gc_stats', 'shards': 1},
       {'name': 'v8testing', 'variant': 'minor_mc', 'shards': 1},
       {'name': 'v8testing', 'variant': 'slow_path', 'shards': 1},
     ],

test/cctest/test-global-object.cc

@@ -59,6 +59,9 @@ TEST(KeysGlobalObject_Regress2764) {
   LocalContext env1;
   v8::HandleScope scope(env1->GetIsolate());
 
+  // Installing an extensions change the global object.
+  if (i::FLAG_gc_stats) return;
+
   // Create second environment.
   v8::Local<Context> env2 = Context::New(env1->GetIsolate());