when resolving symbols with only weak defs, use first def, not last def

[musl] / src / thread / pthread_rwlockattr_getpshared.c

#include "pthread_impl.h"

int pthread_rwlockattr_getpshared(const pthread_rwlockattr_t *a, int *pshared)
{
        *pshared = *(int *)a;
        return 0;
}