Add a test run script to flake.

flake.nix

@@ -59,35 +59,64 @@
           gnumake
           findutils
           binutils
+          cpio
+          gzip
         ];
 
         buildInputs = [
+          pkgs.pkgsStatic.busybox
           mruby
         ];
 
         buildPhase = ''
           make \
             MRUBY_CFLAGS="-I${mruby}/include" \
-            MRUBY_LIBS="-L${mruby}/lib -lmruby"
+            MRUBY_LIBS="-L${mruby}/lib -lmruby" \
+            BUSYBOX="${pkgs.pkgsStatic.busybox}/bin/busybox"
         '';
 
         installPhase = ''
           mkdir -p $out/bin
           cp bin/blade $out/bin/blade
+          cp bin/initramfs.cpio.gz $out/bin/initramfs.cpio.gz
         '';
       };
+
+      run-blade = hostPkgs.writeShellScriptBin "run-blade" ''
+        set -euo pipefail
+        exec ${hostPkgs.qemu}/bin/qemu-system-x86_64 \
+          --enable-kvm \
+          -m 512M \
+          -smp 2 \
+          -kernel "${hostPkgs.linux}/bzImage" \
+          -initrd ${blade}/bin/initramfs.cpio.gz \
+          -append "console=ttyS0 rdinit=/init" \
+          -nographic
+      '';
     in
     {
       packages.${system} = {
         default = blade;
         blade = blade;
         mruby = mruby;
+        run-blade = run-blade;
       };
 
-      devShells.${system}.default = hostPkgs.mkShell {
+      apps.${system} = {
+        default = {
+          type = "app";
+          program = "${run-blade}/bin/run-blade";
+        };
+      };
+
+      devShells.${system}.default = pkgs.mkShell {
         inputsFrom = [ blade ];
 
         packages = with hostPkgs; [
+          linux
+          qemu
+          cpio
+          gzip
           clang-tools
           pkg-config
           ccache
@@ -105,6 +134,8 @@
 
           export MRUBY_CFLAGS=-I${mruby}/include
           export MRUBY_LIBS="-L${mruby}/lib -lmruby"
+          export BUSYBOX="${pkgs.pkgsStatic.busybox}/bin/busybox"
+          export LINUX="${hostPkgs.linux}/bzImage"
         '';
       };
     };