apr-util: Fixup apu-1-config

apu-1-config --ldflags is giving broken output on the fixed-output
dependencies. This broke serf build since db was split to multiple
outputs.

https://nix-cache.s3.amazonaws.com/log/q35s5jba6p6dpdqlfn9qgy5w0hpa506v-serf-1.3.9.drv

pkgs/development/libraries/apr-util/default.nix

@@ -44,7 +44,7 @@ stdenv.mkDerivation rec {
     ++ optional stdenv.isFreeBSD cyrus_sasl;
 
   postInstall = ''
-    for f in $out/lib/*.la $out/lib/apr-util-1/*.la; do
+    for f in $out/lib/*.la $out/lib/apr-util-1/*.la $dev/bin/apu-1-config; do
       substituteInPlace $f \
         --replace "${expat.dev}/lib" "${expat.out}/lib" \
         --replace "${db.dev}/lib" "${db.out}/lib" \