Modify sv_onexec hook to return error.

[dchagin]

Summary

Temporary add stubs to the Linux emulation layer which calls the existing hook.

[kib]

sys/kern/kern_exec.c

1155

At this point, error is KERN_SUCCESS, which is some Mach error code. We never assume that it has zero value. Please replace this fragment by e.g. the following

return (sv->sv_onexec != NULL ? sv->sv_onexec(p, imgp) : 0);

[dchagin]

fixed, i missied that KERN_SUCCESS != 0

[kib]

KERN_SUCCESS is 0, but it is undesirable to depend on that.