When building with USE=duktape, netsurf uses "xxd -i" from vim, which is why vim-core is in BDEPEND. Vim is an annoying dependency, however, and Greg KH wrote a small replacement script for it that's available in Gentoo as dev-util/xxdi.
I'm not 100% sure how this should be done. we can probably add something to the upstream makefile like
XXDI := xxd -i
and then override it in Gentoo with
or something like that if xxdi is installed but vim-core is not.