build/boot/*: unified main() function

The *same* main() function is now used on both scripts.

However, merging both scripts together would be less efficient
on sloccount, and would be error-prone. The purpose of having
roms_helper is that the variables get re-initialised the same
way each time, for each board, automatically.

Signed-off-by: Leah Rowe <leah@libreboot.org>

include/boot.sh

@@ -0,0 +1,41 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
+# SPDX-FileCopyrightText: 2022 Caleb La Grange <thonkpeasant@protonmail.com>
+# SPDX-FileCopyrightText: 2022 Ferass El Hafidi <vitali64pmemail@protonmail.com>
+# SPDX-FileCopyrightText: 2023 Leah Rowe <leah@libreboot.org>
+
+board=""
+boards=""
+displaymodes=""
+payloads=""
+keyboard_layouts=""
+
+main()
+{
+	[ $# -lt 1 ] && usage && err "target not specified"
+
+	first="${1}"
+	[ "${first}" = "help" ] && usage && exit 0
+	[ "${first}" = "list" ] && \
+	    listitems config/coreboot && exit 0
+
+	while [ $# -gt 0 ]; do
+		case ${1} in
+		-d)
+			displaymodes="${2} ${displaymodes}"
+			shift ;;
+		-p)
+			payloads="${2} ${payloads}"
+			shift ;;
+		-k)
+			keyboard_layouts="${2} ${keyboard_layouts}"
+			shift ;;
+		all)
+			first="all" ;;
+		*)
+			boards="${1} ${boards}" ;;
+		esac
+		shift
+	done
+
+	handle_targets
+}