🚀 go-pugleaf

When I try to compile this I get an error message that seems to becoming
from the use of "struct ucontext."   I get the message in user.h.
I am running SVR4, but I ran the script to fix up the header files.
Does anyone out there have a clue?   Thanks.

#define	KERNEL
#include <sys/types.h>
#include <sys/signal.h>
#include <sys/param.h>
#include <sys/dir.h>
#include <sys/immu.h>
#include <sys/region.h>
#include <sys/ucontext.h>
#include <sys/errno.h>
#include <sys/tty.h>
#include <sys/sysmacros.h>
#include <sys/ppio.h>
#include <fcntl.h>
#include <sys/user.h>

main()
{
}