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.

modules/arch/aarch64.nix

@@ -0,0 +1,16 @@
+{ lib, pkgs, config, ...}:
+{
+  config = {
+    kernel.config = {
+      CPU_LITTLE_ENDIAN= "y";
+      CPU_BIG_ENDIAN= "n";
+      # CMDLINE_FROM_BOOTLOADER availability is conditional
+      # on CMDLINE being set to something non-empty
+      CMDLINE="\"console=ttyAMA0\"";
+      CMDLINE_FROM_BOOTLOADER = "y";
+    };
+    boot.commandLine = [
+      "console=ttyAMA0,38400"
+    ];
+  };
+}