unix: add Fchmodat on OpenBSD

Change-Id: If7868a3d43eed266496db8a0e2af908de77362eb
Reviewed-on: https://go-review.googlesource.com/101576
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/unix/zsyscall_openbsd_arm.go b/unix/zsyscall_openbsd_arm.go
index 6a7fe67..59258b0 100644
--- a/unix/zsyscall_openbsd_arm.go
+++ b/unix/zsyscall_openbsd_arm.go
@@ -599,6 +599,21 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Fchmodat(dirfd int, path string, mode uint32, flags int) (err error) {
+	var _p0 *byte
+	_p0, err = BytePtrFromString(path)
+	if err != nil {
+		return
+	}
+	_, _, e1 := Syscall6(SYS_FCHMODAT, uintptr(dirfd), uintptr(unsafe.Pointer(_p0)), uintptr(mode), uintptr(flags), 0, 0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Fchown(fd int, uid int, gid int) (err error) {
 	_, _, e1 := Syscall(SYS_FCHOWN, uintptr(fd), uintptr(uid), uintptr(gid))
 	if e1 != 0 {