utils/ruby.sh: fix error with older Bash
utils/ruby.sh: fix error with older Bash

Fixes #12472.

JCount/brew,JCount/brew,Homebrew/brew,nandub/brew,JCount/brew,MikeMcQuaid/brew,JCount/brew,Homebrew/brew,Homebrew/brew,nandub/brew,nandub/brew,MikeMcQuaid/brew,MikeMcQuaid/brew,MikeMcQuaid/brew,Homebrew/brew,nandub/brew