toolchain-utils: Temporarily uses chrome head

This is to test pattern initialization on nightly and rotation builders. Will be reverted later.

BUG=None

TEST=None

Change-Id: Id197e36cb8537d9d58f170f6b1b1ccb9cf836dc7
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/1644924
Reviewed-by: Tiancong Wang <tcwang@google.com>
Commit-Queue: Jian Cai <jiancai@google.com>
Tested-by: Jian Cai <jiancai@google.com>
diff --git a/buildbot_test_toolchains.py b/buildbot_test_toolchains.py
index c2d8873..c1de155 100755
--- a/buildbot_test_toolchains.py
+++ b/buildbot_test_toolchains.py
@@ -252,7 +252,7 @@
         self._chromeos_root,
         self._build,
         self._patches,
-        tryjob_flags=['--notests'],
+        tryjob_flags=['--notests', '--chrome_version=HEAD'],
         build_toolchain=True)
 
     print('trybot_url: \