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

[musl] / src / thread / pthread_barrierattr_getpshared.c

#include "pthread_impl.h"

int pthread_barrierattr_getpshared(const pthread_barrierattr_t *a, int *pshared)
{
        *pshared = *a;
        return 0;
}