It checks for sys-devel/gettext (tries to run some binaries from it) in its configure phase, probably because gettext is needed by dev-util/intltool, which is a dependency of libgpod. Thus sys-devel/gettext should be explicitly listed as libgpod build dependency. I ran into a problem with that when update of dev-libs/icu broke both libgpod and and gettext, and revdep-rebuild tried to emerge first libgpod and then gettext, and libgpod obviously failed.
dev-util/intltool in DEPEND already takes care of it, but yeah, implicit deps suck, so dep to sys-devel/gettext added closing