turn run-qemu.sh script into mips-vm buildEnv command

pkgs/mips-vm/default.nix

@@ -0,0 +1,11 @@
+{
+  qemu
+, writeShellScriptBin
+, stdenv
+, lib
+}:
+writeShellScriptBin "mips-vm"
+  ''
+     export PATH="${lib.makeBinPath [qemu]}:$PATH"
+     ${builtins.readFile ./mips-vm.sh}
+  ''

pkgs/mips-vm/mips-vm.sh

@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+
+usage(){
+    echo "usage: $(basename $0) [--background /path/to/state_directory] kernel rootimg"
+    echo -e "\nWithout --background, use C-p c (not C-a c) to switch to the monitor"
+    exit 1
+}
+
+if test "$1" = "--background" ; then
+    statedir=$2
+    if test -z "$statedir" || ! test -d $statedir ; then
+	usage
+    fi
+    pid="${statedir}/pid"
+    socket="${statedir}/console"
+    monitor="${statedir}/monitor"
+    echo "running in background, socket is $socket, pid $pid"
+    flags="--daemonize --pidfile $pid -serial unix:$socket,server,nowait -monitor unix:$monitor,server,nowait"
+    shift;shift
+else
+    flags="-serial mon:stdio"
+fi
+
+test -n "$2" || usage
+
+
+INIT=${INIT-/bin/init}
+echo $QEMU_OPTIONS
+qemu-system-mips \
+    -M malta -m 256 \
+    -echr 16 \
+    -append "default console=ttyS0,38400n8 panic=10 oops=panic init=$INIT loglevel=8 root=/dev/vda" \
+    -drive file=$2,format=raw,readonly=on,if=virtio \
+    -netdev socket,id=access,mcast=230.0.0.1:1234,localaddr=127.0.0.1 \
+    -device virtio-net-pci,disable-legacy=on,disable-modern=off,netdev=access,mac=ba:ad:1d:ea:21:02 \
+    -netdev socket,id=lan,mcast=230.0.0.1:1235,localaddr=127.0.0.1 \
+    -device virtio-net-pci,disable-legacy=on,disable-modern=off,netdev=lan,mac=ba:ad:1d:ea:21:01 \
+    -kernel $1 -display none $flags ${QEMU_OPTIONS}