Work around tzcode's reliance on signed overflow.

I've mailed the tz list about this, and will switch to whatever upstream
fix comes along as soon as it's available.

Bug: 10310929

(cherry picked from commit 7843d44a59)

Change-Id: I205e2440703444c50cecd91d3458d33613ddbc59

libc/Android.mk

@@ -718,6 +718,8 @@ LOCAL_CFLAGS := \
     -DTZDIR=\"/system/usr/share/zoneinfo\" \
     -DTM_GMTOFF=tm_gmtoff \
     -DUSG_COMPAT=1
+# tzcode currently relies on signed overflow in numerous places (http://b/10310929).
+LOCAL_CFLAGS += -fno-strict-overflow
 LOCAL_C_INCLUDES := $(libc_common_c_includes)
 LOCAL_MODULE := libc_tzcode
 LOCAL_ADDITIONAL_DEPENDENCIES := $(LOCAL_PATH)/Android.mk