bootable aarch64 liminux with qemu

I may have broken the run-liminix-vm command a bit for MIPS due to
necessary changes in how we pass the command line.  If CI isn't green
for this commit and youre trying the worked examples, I suggest
reverting to the commit before this one.

devices/qemu-aarch64/default.nix

@@ -0,0 +1,69 @@
+# This "device" generates images that can be used with the QEMU
+# emulator. The default output is a directory containing separate
+# kernel ("Image" format) and root filesystem (squashfs or jffs2)
+# images
+{
+  system = {
+    crossSystem = {
+      config = "aarch64-unknown-linux-musl";
+    };
+  };
+
+  module = {pkgs, config, ... }: {
+    imports = [ ../../modules/arch/aarch64.nix ];
+    kernel = {
+      src = pkgs.pkgsBuildBuild.fetchurl {
+        name = "linux.tar.gz";
+        url = "https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.15.71.tar.gz";
+        hash = "sha256-yhO2cXIeIgUxkSZf/4aAsF11uxyh+UUZu6D1h92vCD8=";
+      };
+      config = {
+        VIRTUALIZATION = "y";
+        PCI_HOST_GENERIC="y";
+
+        MTD = "y";
+        MTD_BLOCK2MTD = "y";
+        MTD_BLKDEVS = "y";
+        MTD_BLOCK = "y";
+
+        VIRTIO_MENU = "y";
+        PCI = "y";
+        VIRTIO_PCI = "y";
+        BLOCK = "y";
+        VIRTIO_BLK = "y";
+        NETDEVICES = "y";
+        VIRTIO_NET = "y";
+
+        SERIAL_EARLYCON_ARM_SEMIHOST = "y"; # earlycon=smh
+        SERIAL_AMBA_PL011 = "y";
+        SERIAL_AMBA_PL011_CONSOLE = "y";
+      };
+    };
+    hardware =
+      let
+        mac80211 =  pkgs.mac80211.override {
+          drivers = ["mac80211_hwsim"];
+          klibBuild = config.system.outputs.kernel.modulesupport;
+        };
+      in {
+        defaultOutput = "vmroot";
+        loadAddress = "0x0";
+        entryPoint  = "0x0";
+        rootDevice = "/dev/mtdblock0";
+
+        flash.eraseBlockSize = "65536"; # c.f. pkgs/mips-vm/mips-vm.sh
+        networkInterfaces =
+          let inherit (config.system.service.network) link;
+          in {
+            wan = link.build { ifname = "eth0"; };
+            lan = link.build { ifname = "eth1"; };
+
+            wlan_24 = link.build {
+              ifname = "wlan0";
+              dependencies = [ mac80211 ];
+            };
+          };
+      };
+
+  };
+}

devices/qemu/default.nix

@@ -49,6 +49,7 @@
         };
       in {
         defaultOutput = "vmroot";
+        rootDevice = "/dev/mtdblock0";
         flash.eraseBlockSize = "65536"; # c.f. pkgs/run-liminix-vm/run-liminix-vm.sh
         networkInterfaces =
           let inherit (config.system.service.network) link;