[toolchain-utils] Add --hwtest flag to rotating tester builds.

The rotating testers need to add --hwtest to the trybot builds to
get the hwtests to actually run.  This CL adds that flag.

BUG=None
TEST=Tested in role account.

Change-Id: I6ef93f529b6616dd8d1c357743593ed369d1022a
Reviewed-on: https://chrome-internal-review.googlesource.com/295075
Commit-Ready: Caroline Tice <cmtice@google.com>
Tested-by: Caroline Tice <cmtice@google.com>
Reviewed-by: Ting-Yuan Huang <laszio@google.com>
diff --git a/buildbot_test_llvm.py b/buildbot_test_llvm.py
index 69932e5..479a255 100755
--- a/buildbot_test_llvm.py
+++ b/buildbot_test_llvm.py
@@ -83,12 +83,16 @@
     Launch trybot, get image names, create crosperf experiment file, run
     crosperf, and copy images into seven-day report directories.
     """
+    flags = ['--hwtest']
     date_str = datetime.date.today()
     description = 'master_%s_%s_%s' % (self._patches_string, self._build,
                                        date_str)
-    trybot_image = buildbot_utils.GetTrybotImage(self._chromeos_root,
-                                                 self._build, self._patches,
-                                                 description)
+    trybot_image = buildbot_utils.GetTrybotImage(
+        self._chromeos_root,
+        self._build,
+        self._patches,
+        description,
+        other_flags=flags)
     if len(trybot_image) == 0:
       self._l.LogError('Unable to find trybot_image for %s!' % description)
       return 1