Turn on build/header_guard in cpplint.
Set the correct root path in CPPLINT.cfg and fix existing violations.
Test: tools/repohooks/tools/cpplint.py --quiet system/update_engine/**/*.h
Change-Id: I37812854a68116c69bcef28f8b15856b89a07c4d
diff --git a/CPPLINT.cfg b/CPPLINT.cfg
index 3dd0f35..259fb2f 100644
--- a/CPPLINT.cfg
+++ b/CPPLINT.cfg
@@ -1,3 +1,7 @@
# This should be kept in sync with platform2/CPPLINT.cfg
set noparent
-filter=-build/include_order,+build/include_alpha,-build/header_guard
+
+# Header guard should start with UPDATE_ENGINE_
+root=..
+
+filter=-build/include_order,+build/include_alpha