Here is a WIP patchset creating a 'font-build-system', and packaging a
few font packages with it. I just copied the emacs-build-system and made
necessary changes. Please review and provide feedback.

Currently, the font-build-system only installs ttf and otf files to
/share/fonts/truetype and /share/fonts/opentype respectively. It does
not install any documentation. But, do we really need to install README
files, a copy of the license, etc.?