patchelf: build-script reviewed

System/patchelf/build

@@ -2,5 +2,11 @@
 
 # :FIXME: needs review
 
-pbuild::set_download_url "https://nixos.org/releases/$P/$P-$V/$P-$V.tar.bz2"
-pbuils::add_to_group 'System'
+pbuild::set_download_url "https://github.com/NixOS/$P/archive/$V.tar.gz" "$P-$V.tar.gz"
+
+pbuild::add_to_group 'System'
+
+pbuild::post_prep() {
+	cd "${SRC_DIR}"
+	./bootstrap.sh
+}