Use -Werror in external/smali

* Suppress existing warnings.

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: I3a4516655f19683323dbaa2801a9af930fbd5409
diff --git a/deodexerant/Android.mk b/deodexerant/Android.mk
index 46a9dba..34585fa 100644
--- a/deodexerant/Android.mk
+++ b/deodexerant/Android.mk
@@ -39,6 +39,12 @@
 
 LOCAL_MODULE_TAGS := optional
 
+LOCAL_CFLAGS := \
+    -Wall -Werror \
+    -Wno-incompatible-pointer-types-discards-qualifiers \
+    -Wno-main-return-type \
+    -Wno-unused-parameter \
+
 LOCAL_LDFLAGS := -Wl,--hash-style=sysv
 
 include $(BUILD_EXECUTABLE)