Add redoxer.sh script to simplify running tests on redox

redoxer.sh

+#!/usr/bin/env bash
+
+set -e
+
+if [[ "$(cargo install --list | grep '^redoxer ')" != "redoxer "* ]]
+then
+    cargo install redoxer
+fi
+
+if [ ! -d "$HOME/.redoxer/toolchain" ]
+then
+    redoxer toolchain
+fi
+
+export CARGO_TEST="redoxer"
+export TEST_RUNNER="redoxer exec --folder . -- sh --"
+redoxer env make "$@"