uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>

nixos/lib/test-driver/test_driver/vlan.py

@@ -0,0 +1,58 @@
+from pathlib import Path
+import io
+import os
+import pty
+import subprocess
+
+from test_driver.logger import rootlog
+
+
+class VLan:
+    """This class handles a VLAN that the run-vm scripts identify via its
+    number handles. The network's lifetime equals the object's lifetime.
+    """
+
+    nr: int
+    socket_dir: Path
+
+    process: subprocess.Popen
+    pid: int
+    fd: io.TextIOBase
+
+    def __repr__(self) -> str:
+        return f"<Vlan Nr. {self.nr}>"
+
+    def __init__(self, nr: int, tmp_dir: Path):
+        self.nr = nr
+        self.socket_dir = tmp_dir / f"vde{self.nr}.ctl"
+
+        # TODO: don't side-effect environment here
+        os.environ[f"QEMU_VDE_SOCKET_{self.nr}"] = str(self.socket_dir)
+
+        rootlog.info("start vlan")
+        pty_master, pty_slave = pty.openpty()
+
+        self.process = subprocess.Popen(
+            ["vde_switch", "-s", self.socket_dir, "--dirmode", "0700"],
+            stdin=pty_slave,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            shell=False,
+        )
+        self.pid = self.process.pid
+        self.fd = os.fdopen(pty_master, "w")
+        self.fd.write("version\n")
+
+        # TODO: perl version checks if this can be read from
+        # an if not, dies. we could hang here forever. Fix it.
+        assert self.process.stdout is not None
+        self.process.stdout.readline()
+        if not (self.socket_dir / "ctl").exists():
+            rootlog.error("cannot start vde_switch")
+
+        rootlog.info(f"running vlan (pid {self.pid})")
+
+    def __del__(self) -> None:
+        rootlog.info(f"kill vlan (pid {self.pid})")
+        self.fd.close()
+        self.process.terminate()