Suppress shift-count-overflow warning on Darwin.

Bug: http://b/66996870
Test: Builds on Linux (Darwin not available for testing).
Change-Id: Ie34424a378ab15c0d7abce2bd173c7c61fa41f2a
diff --git a/Android.mk b/Android.mk
index cb8753b..a0a3cfb 100644
--- a/Android.mk
+++ b/Android.mk
@@ -15,8 +15,7 @@
 LOCAL_PATH:= $(call my-dir)
 
 ifeq ($(HOST_OS),darwin)
-# No -Werror for darwin yet. Need to fix/suppress more warnings.
-BISON_WERROR :=
+BISON_WERROR := -Wno-shift-count-overflow
 else
 BISON_WERROR := -Werror
 endif