@pbs0512 i found that this error is caused by NDK compatibility issue, can refer to this issue for detail information.
Indeed, the arch-arm/usr/include/signal.h header up to "android-19" contained:
/* differentiater between sysv and bsd behaviour 8*/
extern __sighandler_t sysv_signal(int, __sighandler_t);
extern __sighandler_t bsd_signal(int, __sighandler_t);
/* the default is bsd */
static __inline__ __sighandler_t signal(int s, __sighandler_t f)
but starting at "android-21" (there is no android-20) has just:
extern sighandler_t signal(int, sighandler_t);
So it looks that stdlib would have to use different symbols depending on which version of Android SDK it was targeting.