libtool.eclass: Use app-portage/elt-patches to provide patch files

eclass/libtool.eclass

@@ -1,4 +1,4 @@
-# Copyright 1999-2014 Gentoo Foundation
+# Copyright 1999-2017 Gentoo Foundation
 # Distributed under the terms of the GNU General Public License v2
 
 # @ECLASS: libtool.eclass
@@ -16,18 +16,10 @@
 if [[ -z ${_LIBTOOL_ECLASS} ]]; then
 _LIBTOOL_ECLASS=1
 
-# If an overlay has eclass overrides, but doesn't actually override the
-# libtool.eclass, we'll have ECLASSDIR pointing to the active overlay's
-# eclass/ dir, but libtool.eclass is still in the main Gentoo tree.  So
-# add a check to locate the ELT-patches/ regardless of what's going on.
-# Note: Duplicated in eutils.eclass.
-_LIBTOOL_ECLASSDIR_LOCAL=${BASH_SOURCE[0]%/*}
+DEPEND=">=app-portage/elt-patches-20170317"
+
 libtool_elt_patch_dir() {
-	local d="${ECLASSDIR}/ELT-patches"
-	if [[ ! -d ${d} ]] ; then
-		d="${_LIBTOOL_ECLASSDIR_LOCAL}/ELT-patches"
-	fi
-	echo "${d}"
+	echo "${EPREFIX}/usr/share/elt-patches"
 }
 
 inherit multilib toolchain-funcs