Build tzcode with -Werror.

Parts of this are just getting us in sync with upstream, but the
'const' stuff is our own mess. We should kill the *_tz functions
and lose this difference from upstream.

Change-Id: I17d26534ed3f54667143d78147a8c53be56d7b33
diff --git a/libc/Android.mk b/libc/Android.mk
index 2747a3e..4ed9468 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -597,6 +597,7 @@
 # Include timezone and daylight globals.
 LOCAL_CFLAGS += -DUSG_COMPAT=1
 LOCAL_CFLAGS += -DNO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU
+LOCAL_CFLAGS += -Dlint -Werror
 
 LOCAL_CONLYFLAGS := $(libc_common_conlyflags)
 LOCAL_CPPFLAGS := $(libc_common_cppflags)