Turn on -Werror for ssp.cpp.

libc_bionic.a is already compiled -Werror, but this one file gets
compiled into its own library because it needs to be compiled with
-fno-stack-protector.

Change-Id: I273c535ab5c73ccaccbcf793fda1f788a2589abe
diff --git a/libc/Android.mk b/libc/Android.mk
index 4130e25..f78cf2c 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -726,7 +726,7 @@
 include $(CLEAR_VARS)
 
 LOCAL_SRC_FILES := bionic/ssp.cpp
-LOCAL_CFLAGS := $(libc_common_cflags) -fno-stack-protector
+LOCAL_CFLAGS := $(libc_common_cflags) -fno-stack-protector -Werror
 LOCAL_C_INCLUDES := $(libc_common_c_includes)
 LOCAL_MODULE := libbionic_ssp
 LOCAL_ADDITIONAL_DEPENDENCIES := $(LOCAL_PATH)/Android.mk