Remove windows code and simplify linux

Windows will not use containerd and its just unused code and unneed
complexity to keep it all around.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

runtime/process.go

@@ -70,7 +70,21 @@ func newProcess(config *processConfig) (*process, error) {
 	}
 	defer f.Close()
 
-	ps := populateProcessStateForEncoding(config, uid, gid)
+	ps := ProcessState{
+		ProcessSpec: config.processSpec,
+		Exec:        config.exec,
+		PlatformProcessState: PlatformProcessState{
+			Checkpoint: config.checkpoint,
+			RootUID:    uid,
+			RootGID:    gid,
+		},
+		Stdin:       config.stdio.Stdin,
+		Stdout:      config.stdio.Stdout,
+		Stderr:      config.stdio.Stderr,
+		RuntimeArgs: config.c.runtimeArgs,
+		NoPivotRoot: config.c.noPivotRoot,
+	}
+
 	if err := json.NewEncoder(f).Encode(ps); err != nil {
 		return nil, err
 	}
@@ -204,3 +218,24 @@ func (p *process) getPidFromFile() (int, error) {
 	p.pid = i
 	return i, nil
 }
+
+func getExitPipe(path string) (*os.File, error) {
+	if err := syscall.Mkfifo(path, 0755); err != nil && !os.IsExist(err) {
+		return nil, err
+	}
+	// add NONBLOCK in case the other side has already closed or else
+	// this function would never return
+	return os.OpenFile(path, syscall.O_RDONLY|syscall.O_NONBLOCK, 0)
+}
+
+func getControlPipe(path string) (*os.File, error) {
+	if err := syscall.Mkfifo(path, 0755); err != nil && !os.IsExist(err) {
+		return nil, err
+	}
+	return os.OpenFile(path, syscall.O_RDWR|syscall.O_NONBLOCK, 0)
+}
+
+// Signal sends the provided signal to the process
+func (p *process) Signal(s os.Signal) error {
+	return syscall.Kill(p.pid, s.(syscall.Signal))
+}