Create taler-config wrapper around gnunet-config

The wrapper uses LD_PRELOAD to make sure that paths are adjusted
for taler.

src/util/Makefile.am

@@ -15,6 +15,18 @@ pkgcfg_DATA = \
 EXTRA_DIST = \
   paths.conf
 
+dist_bin_SCRIPTS = taler-config
+
+# See https://www.gnu.org/software/autoconf/manual/autoconf-2.63/html_node/Installation-Directory-Variables.html
+# for and explanation and why this ugliness is necessary.
+edit = sed -e 's|@libdir[@]|$(libdir)|g'
+taler-config: Makefile $(srcdir)/taler-config.in
+	rm -f $@ $@.tmp
+	$(edit) '$(srcdir)/$@.in' >$@.tmp
+	chmod +x $@.tmp
+	chmod a-w $@.tmp
+	mv $@.tmp $@
+
 if WALLET_ONLY
 lib_LTLIBRARIES = \
   libtalerutil_wallet.la

src/util/taler-config.in

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+
+if ! type gnunet-config >/dev/null; then
+  echo "$0 needs gnunet-config to be installed"
+  exit 1
+fi
+
+# FIXME: not very portable ...
+export LD_PRELOAD=@libdir@/libtalerutil.so
+exec gnunet-config "$@"