makeNugetSource: symlink files instead of copying them

this reduces the closure size of the resulting derivation drastically

pkgs/build-support/dotnet/make-nuget-source/default.nix

@@ -17,7 +17,7 @@ let
       # use -L to follow symbolic links. When `projectReferences` is used in
       # buildDotnetModule, one of the deps will be a symlink farm.
       find -L ${lib.concatStringsSep " " deps} -type f -name '*.nupkg' -exec \
-        cp --no-clobber '{}' $out/lib ';'
+        ln -s '{}' -t $out/lib ';'
 
       # Generates a list of all licenses' spdx ids, if available.
       # Note that this currently ignores any license provided in plain text (e.g. "LICENSE.txt")