Add an explicit "exit 0" to the shell scripts. This worked more or less by

coincidence before since shell scripts return the exit code of the last
command run if there is no explicit exit statement.

.github/checks/sorted_codeopt.sh

@@ -66,3 +66,4 @@ function checkarray
 find "$CHECK_DIR" -name \*.\[ch\] -print | while read N; do
     grep -q "BEGIN DECL SORTED_CODEOPT.SH" "$N" && checkarray $N
 done
+exit 0