fix(executor/sandbox): non nil stdin

internal/executor/sandbox/executor.go

@@ -103,6 +103,9 @@ func (e *Sandbox) runWithTar(cmds []stage.Cmd, tarData []byte) ([]stage.Executor
 	tarCmd := stage.Cmd{
 		Args:         []string{"/bin/tar", "xf", tarFileName, "-C", "/w"},
 		Env:          cmds[0].Env,
+		Stdin:        &stage.CmdFile{Content: strPtr("")},
+		Stdout:       &stage.CmdFile{Name: strPtr("__tar_stdout"), Max: int64Ptr(1)},
+		Stderr:       &stage.CmdFile{Name: strPtr("__tar_stderr"), Max: int64Ptr(1)},
 		CPULimit:     cmds[0].CPULimit,
 		ClockLimit:   cmds[0].ClockLimit,
 		MemoryLimit:  cmds[0].MemoryLimit,
@@ -326,3 +329,7 @@ func (e *Sandbox) Cleanup() error {
 	}
 	return nil
 }
+
+func strPtr(s string) *string { return &s }
+
+func int64Ptr(i int64) *int64 { return &i }