gnutls: don't propagate -lunistring

This fixes systemd build.  Also put it into the generic expression,
as there's only one version in nixpkgs ATM.

pkgs/development/libraries/gnutls/3.5.nix

@@ -7,6 +7,4 @@ callPackage ./generic.nix (args // rec {
     url = "ftp://ftp.gnutls.org/gcrypt/gnutls/v3.5/gnutls-${version}.tar.xz";
     sha256 = "0l9971841jsfdcvcyhas17sk5rsby6x5vvwcmmj4x3zi9q60zcc2";
   };
-
-  buildInputs = [ libunistring ];
 })

pkgs/development/libraries/gnutls/generic.nix

@@ -1,6 +1,6 @@
 { lib, fetchurl, stdenv, zlib, lzo, libtasn1, nettle, pkgconfig, lzip
 , guileBindings, guile, perl, gmp, autogen, libidn, p11_kit, unbound, libiconv
-, tpmSupport ? false, trousers, nettools, bash
+, tpmSupport ? false, trousers, nettools, libunistring
 
 # Version dependent args
 , version, src, patches ? [], postPatch ? "", nativeBuildInputs ? []
@@ -37,7 +37,7 @@ stdenv.mkDerivation {
 
   enableParallelBuilding = true;
 
-  buildInputs = [ lzo lzip libtasn1 libidn p11_kit zlib gmp autogen ]
+  buildInputs = [ lzo lzip libtasn1 libidn p11_kit zlib gmp autogen libunistring ]
     ++ lib.optional doCheck nettools
     ++ lib.optional (stdenv.isFreeBSD || stdenv.isDarwin) libiconv
     ++ lib.optional (tpmSupport && stdenv.isLinux) trousers
@@ -58,6 +58,9 @@ stdenv.mkDerivation {
         -e 's,-L${gmp.dev}/lib,-L${gmp.out}/lib,' \
         -e 's,-lgmp,-L${gmp.out}/lib -lgmp,' \
         -i $out/lib/*.la "$dev/lib/pkgconfig/gnutls.pc"
+    # It seems only useful for static linking but basically noone does that.
+    substituteInPlace "$out/lib/libgnutls.la" \
+      --replace "-lunistring" ""
   '';
 
   meta = with lib; {