vfork use waitpid hang father process,
but waitpid release child processs information by default.
So when user call wait, it return errno 10.
Signed-off-by: yangyalei <yangyalei@xiaomi.com>
1. as we can use fork to implement vfork, so we rename the vfork to
fork, and use the fork method as the base to implement vfork method
2. create the vfork function as a libc function based on fork
function
Signed-off-by: guoshichao <guoshichao@xiaomi.com>
