Don't compile with GIF support.

Emacs source depends on libgif, which is an abandoned project[1]. Some
distros, such as Arch Linux patch Emacs to support giflib[2]. For EVM, I
think it's sufficient to compile without GIF support.

[1] https://bugs.archlinux.org/task/8927?project=1&pagenum=11
[2] https://projects.archlinux.org/svntogit/packages.git/commit/trunk?h=packages/emacs&id=b7683f99af92c2387e6a01d7e386453223e0f4e7