ext: move syscall wrappers from container

These are generally useful, and none of them are container-specific. Syscalls subtle to use and requiring container-specific setup remains in container.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/mount.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	. "syscall"
 
+	"hakurei.app/ext"
 	"hakurei.app/message"
 	"hakurei.app/vfs"
 )
@@ -115,7 +116,7 @@ func (p *procPaths) remount(msg message.Msg, target string, flags uintptr) error
 	var targetKFinal string
 	{
 		var destFd int
-		if err := IgnoringEINTR(func() (err error) {
+		if err := ext.IgnoringEINTR(func() (err error) {
 			destFd, err = p.k.open(targetFinal, O_PATH|O_CLOEXEC, 0)
 			return
 		}); err != nil {