CI: shellcheck: make pmbootstrap ci compatible (MR 12)

.ci/shellcheck.sh

 #!/bin/sh -e
-# Copyright 2021 Oliver Smith
+# Copyright 2023 Oliver Smith
 # Copyright 2022 Dylan Van Assche
 # SPDX-License-Identifier: GPL-3.0-or-later
+# Description: lint all shell scripts
+# https://postmarketos.org/pmb-ci
 
-set -e
-DIR="$(cd "$(dirname "$0")" && pwd -P)"
-cd "$DIR/.."
+DIR="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+if [ "$(id -u)" = 0 ]; then
+	set -x
+	apk -q add shellcheck
+	exec su "${TESTUSER:-build}" -c "sh -e $0"
+fi
 
 # Shell: shellcheck
 sh_files="
 	$(find . -path '*.sh')
-
-	$(find . -path '.ci/*.sh')
 "
+
 for file in $sh_files; do
 	echo "Test with shellcheck: $file"
-	cd "$DIR/../$(dirname "$file")"
+	cd "$DIR/$(dirname "$file")"
 	shellcheck -e SC1008 -x "$(basename "$file")"
 done
-

.gitlab-ci.yml

@@ -25,7 +25,7 @@ shellcheck:
   <<: *only-default
   image: alpine:edge
   before_script:
-    - apk -q add shellcheck
+    - adduser -D build
   script:
     - .ci/shellcheck.sh