This fixes linking libfstest/test-fcntl (and others).

As discussed with upstream: https://lists.gnu.org/archive/html/bug-hurd/2020-03/msg00018.html

From 96a9f67a8685e713f25259c18306797d54cc27a5 Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Sat, 14 Mar 2020 11:28:31 +0100
Subject: [PATCH] build: Fix cross build on Guix.

As discussed in https://lists.gnu.org/archive/html/bug-hurd/2020-03/msg00018.html.

* Makeconf (lpath): Add -Wl,-rpath-link=<dir> next to -L<dir>.
---
 Makeconf | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Makeconf b/Makeconf
index 67f7ab1c..f68ff6e3 100644
--- a/Makeconf
+++ b/Makeconf
@@ -325,7 +325,8 @@ _libsubst=${libsubst$(patsubst %,-override,${libsubst-override})}
 
 # Direct the linker where to find shared objects specified in the
 # dependencies of other shared objects it encounters.
-lpath := -L. $(patsubst %,-L%,$(dir $(wildcard ../lib*/lib*.so)))
+lib_dirs := $(dir $(wildcard ../lib*/lib*.so))
+lpath := -L. $(lib_dirs:%=-L%) $(lib_dirs:%=-Wl,-rpath-link=%)
 
 # Main rule to link executables
 #
-- 
2.24.0