libre/iceweasel: Sync with upstream 80.0.1
    
    Also removed leftover flags dropped by upstream in 80.0-1, See:
    https://github.com/archlinux/svntogit-packages/commit/7f7808aed43c21887a9b440005b6aca4e9295b9d#diff-91e904bd64036c9c236ce84542f97781L112
    
    These flags probably should be removed for i686 too, but I was
    not able to build it with or without them anyway.