sys-apps/systemd: Reimplement builddir_ functions

This is to avoid querying pkg-config for this information and
overriding the SYSROOT variable. These hacks seem to be broken with
the change of the pkgconfig implementation.

We know what will the path for the directory of the system units -
it's based on rootprefix that we pass to configure script. So use this
knowledge directly instead of getting it in a roundabout way from
pkg-config file.

sdk_container/src/third_party/coreos-overlay/sys-apps/systemd/systemd-9999.ebuild

@@ -247,6 +247,10 @@ src_configure() {
 	multilib-minimal_src_configure
 }
 
+get_rootprefix() {
+	usex split-usr "${EPREFIX:-/}" "${EPREFIX}/usr"
+}
+
 multilib_src_configure() {
 	local myconf=(
 		--localstatedir="${EPREFIX}/var"
@@ -258,7 +262,7 @@ multilib_src_configure() {
 		# make sure we get /bin:/sbin in PATH
 		$(meson_use split-usr)
 		-Dsplit-bin=true
-		-Drootprefix="$(usex split-usr "${EPREFIX:-/}" "${EPREFIX}/usr")"
+		-Drootprefix="$(get_rootprefix)"
 		-Drootlibdir="${EPREFIX}/usr/$(get_libdir)"
 		# Avoid infinite exec recursion, bug 642724
 		-Dtelinit-path="${EPREFIX}/lib/sysvinit/telinit"
@@ -500,18 +504,18 @@ multilib_src_install_all() {
 	# dropped it.
 }
 
-builddir_systemd_enable_service() {
-    (
-        export SYSROOT="${ED}"
-        systemd_enable_service "$@"
-    )
+builddir_systemd_get_systemunitdir() {
+	echo "$(get_rootprefix)/lib/systemd/system"
 }
 
-builddir_systemd_get_systemunitdir() {
-    (
-        export SYSROOT="${ED}"
-        systemd_get_systemunitdir
-    )
+builddir_systemd_enable_service() {
+	local target=${1}
+	local service=${2}
+	local ud=$(builddir_systemd_get_systemunitdir)
+	local destname=${service##*/}
+
+	dodir "${ud}"/"${target}".wants && \
+	dosym ../"${service}" "${ud}"/"${target}".wants/"${destname}"
 }
 
 migrate_locale() {