Define DEFAULT_TIDY_HEADER_DIRS.

Let clang-tidy report warnings in header files in the
system and current directories but not the external
and vendor directories.

Test: build with WITH_TIDY=1
Change-Id: I1723b8eb95948961fb7164a19989e0a926e5bf8a
diff --git a/core/binary.mk b/core/binary.mk
index fb31890..ad0bbcc 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -1649,7 +1649,7 @@
     endif
     # If tidy flags are not specified, default to check all header files.
     ifeq ($(my_tidy_flags),)
-      my_tidy_flags := -header-filter=.*
+      my_tidy_flags := $(call default_tidy_header_filter,$(LOCAL_PATH))
     endif
   endif
 endif