Compiling for older macos releases?

[Ben Martin]

Hi,
  Sorry for what feels like an FAQ, in a nutshell: If I am using
macports to make packages and want the packages to also run on older
macos releases what do I change?

  I recently got the github version of fontforge to compile on Mountain
Lion but some users are on 10.6/10.7 of macos and have reported issues
running it.

Thanks && sorry for the mac newbie question.