CI: run codespell instead of checkpatch spellcheck

In theory checkpatch.pl should use its spelling.txt to check for spell
errors in the code, but it seems to be broken for some reason. It also
has code to use codespell's dictionaries... but just use codespell
directly.

.ci/codespell.sh

+#!/bin/sh -ex
+# SPDX-License-Identifier: GPL-3.0-or-later
+# Copyright 2023 Oliver Smith
+# Description: find typos
+# https://postmarketos.org/pmb-ci
+
+if [ "$(id -u)" = 0 ]; then
+	set -x
+	apk -q add \
+		py3-codespell
+	exec su "${TESTUSER:-build}" -c "sh -e $0"
+fi
+
+set -x
+
+codespell \
+	--skip="./subprojects,./po" \
+	. \
+	.ci/*

.ci/lint.sh

@@ -9,17 +9,15 @@
 SCRIPT_DIR="$(dirname "$(realpath "$0")")"
 
 # Download checkpatch from linux.git
-cd "$SCRIPT_DIR"
-for f in checkpatch.pl spelling.txt; do
-	if ! [ -e "$SCRIPT_DIR/$f" ]; then
-		url="https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/scripts/$f"
-		echo "Download: $url"
-		wget -q "$url"
-		chmod +x "$f"
-	fi
-done
-
-cd ..
+if ! [ -e "$SCRIPT_DIR/checkpatch.pl" ]; then
+	cd "$SCRIPT_DIR"
+	url="https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/scripts/checkpatch.pl"
+	echo "Download: $url"
+	wget -q "$url"
+	chmod +x "checkpatch.pl"
+	touch spelling.txt
+	cd ..
+fi
 
 # NOTE: giving all files directly as arguments to checkpatch.pl was buggy, so
 # call it once per file for now. See .checkpatch.conf for additional options.

.gitlab-ci.yml

 ---
-image: "alpine:latest"
+image: "alpine:edge"
 
 lint:
   before_script:
@@ -7,6 +7,13 @@ lint:
   script:
     - .ci/lint.sh
 
+codespell:
+  before_script:
+    - "echo 'https://dl-cdn.alpinelinux.org/alpine/edge/testing' >> /etc/apk/repositories"
+    - "adduser -D build"
+  script:
+    - .ci/codespell.sh
+
 build-pmOS:
   before_script:
     - "apk -q add git"