Update libcontainer dependency

vendor/github.com/opencontainers/runc/libcontainer/system/linux.go

@@ -11,6 +11,19 @@ import (
 	"unsafe"
 )
 
+// If arg2 is nonzero, set the "child subreaper" attribute of the
+// calling process; if arg2 is zero, unset the attribute.  When a
+// process is marked as a child subreaper, all of the children
+// that it creates, and their descendants, will be marked as
+// having a subreaper.  In effect, a subreaper fulfills the role
+// of init(1) for its descendant processes.  Upon termination of
+// a process that is orphaned (i.e., its immediate parent has
+// already terminated) and marked as having a subreaper, the
+// nearest still living ancestor subreaper will receive a SIGCHLD
+// signal and be able to wait(2) on the process to discover its
+// termination status.
+const PR_SET_CHILD_SUBREAPER = 36
+
 type ParentDeathSignal int
 
 func (p ParentDeathSignal) Restore() error {
@@ -40,6 +53,14 @@ func Execv(cmd string, args []string, env []string) error {
 	return syscall.Exec(name, args, env)
 }
 
+func Prlimit(pid, resource int, limit syscall.Rlimit) error {
+	_, _, err := syscall.RawSyscall6(syscall.SYS_PRLIMIT64, uintptr(pid), uintptr(resource), uintptr(unsafe.Pointer(&limit)), uintptr(unsafe.Pointer(&limit)), 0, 0)
+	if err != 0 {
+		return err
+	}
+	return nil
+}
+
 func SetParentDeathSignal(sig uintptr) error {
 	if _, _, err := syscall.RawSyscall(syscall.SYS_PRCTL, syscall.PR_SET_PDEATHSIG, sig, 0); err != 0 {
 		return err
@@ -79,17 +100,12 @@ func Setctty() error {
 	return nil
 }
 
-/*
- * Detect whether we are currently running in a user namespace.
- * Copied from github.com/lxc/lxd/shared/util.go
- */
+// RunningInUserNS detects whether we are currently running in a user namespace.
+// Copied from github.com/lxc/lxd/shared/util.go
 func RunningInUserNS() bool {
 	file, err := os.Open("/proc/self/uid_map")
 	if err != nil {
-		/*
-		 * This kernel-provided file only exists if user namespaces are
-		 * supported
-		 */
+		// This kernel-provided file only exists if user namespaces are supported
 		return false
 	}
 	defer file.Close()
@@ -112,3 +128,16 @@ func RunningInUserNS() bool {
 	}
 	return true
 }
+
+// SetSubreaper sets the value i as the subreaper setting for the calling process
+func SetSubreaper(i int) error {
+	return Prctl(PR_SET_CHILD_SUBREAPER, uintptr(i), 0, 0, 0)
+}
+
+func Prctl(option int, arg2, arg3, arg4, arg5 uintptr) (err error) {
+	_, _, e1 := syscall.Syscall6(syscall.SYS_PRCTL, uintptr(option), arg2, arg3, arg4, arg5, 0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}