Adding libsecret to cargo to get cargo login to work (#190)

This makes `cargo:libsecret` work, which is included in the recommended configuration.

See: https://doc.rust-lang.org/cargo/reference/registry-authentication.html#cargolibsecret

lib/mk-component-set.nix

@@ -1,5 +1,6 @@
 # Define component derivations and special treatments.
 { lib, stdenv, stdenvNoCC, gnutar, autoPatchelfHook, bintools, zlib, gccForLibs
+, pkgsHostHost
 # The path to nixpkgs root.
 , path
 , toRustTarget, removeNulls
@@ -139,6 +140,9 @@ let
             wrap "$dst" ${path + "/pkgs/build-support/bintools-wrapper/ld-wrapper.sh"} "$unwrapped"
           done
         fi
+      ''
+      + optionalString (stdenv.isLinux && pname == "cargo") ''
+        patchelf --add-needed ${pkgsHostHost.libsecret}/lib/libsecret-1.so.0 $out/bin/cargo
       '';
 
       env = lib.optionalAttrs (pname == "rustc") {