arch scripts

It took a moment to work out that there is actually no way of
bootstrapping an arch environment without permanently installing things
to the host system! So we just download a live image and unpack it.

Then after that, getting erlang to work was very easy, just install it,
install zx, run. No R26 incompatibility problems, life is good!

arch/enter_environment

@@ -0,0 +1,22 @@
+#!/bin/sh
+
+if test `id -u` -ne 0
+then
+    echo "$0 must be run as root."
+    return
+fi
+
+ROOT=test_environment
+
+if test -e "$ROOT"
+then
+    echo "Using existing environment in $ROOT."
+else
+    ./create_environment
+fi
+
+./cleanup add_mounts
+
+chroot "$ROOT" sudo -iu user "$@"
+
+./cleanup mounts