Fix some warning messages of shellcheck(1)

Fix some warning messages of shellcheck(1)

- SC1090: Can't follow non-constant source. Use a directive to
  specify location.

- SC2125: Brace expansions and globs are literal in assignments.
  Quote it or use an array.

- SC2166: Prefer [ p ] && [ q ] as [ p -a q ] is not well defined.

See <http://www.shellcheck.net>.