the big rebuild - libpng/libtiff
i cannot speak about libtiff but libpng 1.5 rebuild is going to be
difficult. All previous warnings are now fatal and a lot of patching is
I managed to get all patches from gentoo here (thanks gentoo devs!):
Patches also can be found in fedora rawhide and openbsd.
The rebuild is done as usually in staging and at first you won't be able
to build any packages until their dependencies are built first.