Fix shellcheck warnings in shell scripts.

lib/codegen/meta/check.sh

@@ -1,9 +1,10 @@
 #!/bin/bash
 set -euo pipefail
-cd $(dirname "$0")
+topdir=$(dirname "$0")
+cd "$topdir"
 
 function runif {
-    if command -v "$1" > /dev/null; then
+    if type "$1" > /dev/null; then
         echo "   === $1 ==="
         "$@"
     else