Add check for clang-format in pre-preupload hooks

We currently do not check this in update_engine and this causes people sending
patches that have not gone through clang-format. This patch adds a clang-format
preupload hook.

BUG=none
TEST=repo upload

Change-Id: Ia7231cb85b6c952704f030bda74f1e3aa9ee5e0c
Reviewed-on: https://chromium-review.googlesource.com/969062
Commit-Ready: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/PRESUBMIT.cfg b/PRESUBMIT.cfg
index 3b8b271..f2c7831 100644
--- a/PRESUBMIT.cfg
+++ b/PRESUBMIT.cfg
@@ -3,5 +3,6 @@
 hook1=../../../platform2/common-mk/gyplint.py ${PRESUBMIT_FILES}
 
 [Hook Overrides]
+clang_format_check: true
 cros_license_check: false
 aosp_license_check: true