in function bootstrap_tree, when directories are created
         for x in etc  usr/{,s}bin var/tmp var/lib/portage var/log/ 
portage var/db;
         do
                 [[ -d ${ROOT}/${x} ]] || mkdir -p "${ROOT}/${x}"
         done
I think {,s}bin. It breaks the installation of bash, and so $EPREFIX/ 
bin/sh is missing, and that breaks the gcc installation.

And in the bash ebuild, I think that you could had  
CFLAGS_FOR_BUILD="$CFLAGS". I don't know why, but that's the CFLAGS  
using by bash for building.
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