Support swap files in qemu or bare-metal mode

This can help alleviate memory pressure when bootstrapping
with high core counts.

steps/improve/swap.sh

@@ -0,0 +1,19 @@
+
+#!/bin/sh
+#
+# SPDX-FileCopyrightText: 2024 Gábor Stefanik <netrolller.3d@gmail.com>
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+# Set up swap
+
+. /steps/bootstrap.cfg
+. /steps/env
+
+if ! test -f /swapfile
+then
+    echo "Making swap..."
+    dd if=/dev/zero of=/swapfile bs=1M count=${SWAP_SIZE}
+    mkswap /swapfile
+fi
+swapon /swapfile