message: remove `-lrt`, compatible with Windows and MacOS
diff: @@ -6,4 +6,4 @@ Name: DataFrame
  Description: C++ DataFrame -- R's and Pandas DataFrame in modern C++ using native types, continuous memory storage, and no virtual functions.
  Version: @PROJECT_NAME_VERSION@
  Cflags: -I${includedir}
  -Libs: -L${libdir} -lDataFrame -lrt
  +Libs: -L${libdir} -lDataFrame
  