How can I limit a "Run Script" build phase to my release configuration?

if [ "${CONFIGURATION}" = "Release" ]; then
  echo Do something really release-like
fi

The script will run at the end of every configuration, but it won't do anything in this case unless the configuration is Release (assuming everything it does is contained within the test block).

The easiest way to do this, is checking the "Run script only when installing" checkbox.