dosfstools: Enable compat symlinks

Create these symlinks, since NixOS (and other users) can still be using
the old names:
    dosfsck -> fsck.fat
    dosfslabel -> fatlabel
    fsck.msdos -> fsck.fat
    fsck.vfat -> fsck.fat
    mkdosfs -> mkfs.fat
    mkfs.msdos -> mkfs.fat
    mkfs.vfat -> mkfs.fat

While at it, kill the makeFlags which seems unnecessary as it seems
to use a standard Autotools build (maybe this is a new thing).