ci: move shellcheck options to .shellcheckrc

That way, IDEs get to have the same behaviour as the CI

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31826>

.gitlab-ci/run-shellcheck.sh

@@ -13,7 +13,7 @@ anyfailed=0
 
 while IFS= read -r -d $'' file; do
     if is_bash "$file" ; then
-        if ! shellcheck -x -W0 -s bash "$file"; then
+        if ! shellcheck "$file"; then
             anyfailed=1
         fi
     fi

.gitlab-ci/test/gitlab-ci.yml

@@ -65,6 +65,7 @@ yaml-toml-shell-test:
       changes: &toml_lint_files
         - .gitlab-ci/test/gitlab-ci.yml
         - .gitlab-ci/**/*.sh
+        - .shellcheckrc
         - bin/toml_lint.py
         - src/**/ci/*.toml
       when: on_success

.shellcheckrc

@@ -0,0 +1,10 @@
+# Allow using `source` to execute the contents of other files than the one
+# being checked.
+external-sources=true
+
+# Do not print links to wiki pages explaining why this is an issue.
+wiki-link-count=0
+
+# All shell scripts are being run using bash, even if they are lacking
+# a shebang.
+shell=bash