Enabling thumb mode for your ARM binaries

While cross compiling binaries for maemo, I wanted to enable the thumb compile option, but didnt really knew how to, jumped to #maemo irc, and there I could quickly get the info I needed. (Thanks to tko), so I documented it (I hope it will act as a starter, for other to add info). It would also be nice if this kind of info is also available in official maemo documentation