ruby-modules/gem-config: patch mathematical gem for Darwin (#384539)

      rpath="$(patchelf --print-rpath "$soPath")"

      patchelf --set-rpath "${lib.makeLibraryPath [ lasem glib cairo ]}:$rpath" "$soPath"

      patchelf --replace-needed liblasem.so liblasem-0.4.so "$soPath"

    ''  + lib.optionalString stdenv.hostPlatform.isDarwin ''

      soPath="$out/${ruby.gemPath}/gems/mathematical-${attrs.version}/lib/mathematical/mathematical.bundle"

      install_name_tool -add_rpath "${lib.makeLibraryPath [ lasem glib cairo ]}/lib" "$soPath"

      install_name_tool -change @rpath/liblasem.dylib "${lib.getLib lasem}/lib/liblasem-0.4.dylib" "$soPath"

    '';

  };