tests: add USB storage test

tests/default.nix

@@ -19,6 +19,7 @@ let
         ./hello.nix
         ./log.nix
         ./nim.nix
+        ./usb.nix
         ./vmm_x86.nix
       ];
 

tests/usb.nix

@@ -0,0 +1,16 @@
+{
+  name = "usb";
+  machine = { pkgs, ... }: {
+    genode.boot.storeBackend = "fs";
+    hardware.genode.usb.enable = true;
+    hardware.genode.usb.storage.enable = true;
+    genode.init.children.hello = {
+      package = pkgs.hello;
+      configFile = ./hello.dhall;
+    };
+  };
+  testScript = ''
+    start_all()
+    machine.wait_until_serial_output("Hello, world!")
+  '';
+}