Adapting Compiler Options?

I was wondering what the most straightforward way is to adapt the compiler options. In particular, I would like to add an include '-I' option to point to the current directory, ie. '-I.' . I don't mind editing (and maintaining) a makefile, but I don't seem to be able to find the corresponding (template) file in the Arduino IDE installation tree, and maybe there's an easier method anyway. I use IDE version 1.0 on OS X.

Thanks for any help.