[builder] Does it also work for FontForge projects?

[felipesanches]

@m4rc1e, On a checkout of https://github.com/Typedesigners/Anta-Regular and after copying the Makefile and the scripts/ dir from the googlefonts-template I tried to run make build and got this:

I did not investigate it further, but it may be related to the project being developed on FontForge. Does the gftools builder support building from .sfd project files?