The default src_compile() function in current versions of portage only executes econf if ${WORKDIR}/configure is executable. I would be better if it supported ${ECONF_SOURCE}/configure. This suggestion originated in bug 178378.
Created attachment 132462 [details, diff] make the default src_compile() support ECONF_SOURCE if EAPI > 0 This patch has been in trunk for awhile but it's never been released.
This is supported in >=sys-apps/portage-2.1.3.12 when EAPI > 0.