GenerateExportHeader: support exporting from OBJECT libraries

Modules/GenerateExportHeader.cmake

@@ -363,6 +363,7 @@ function(GENERATE_EXPORT_HEADER TARGET_LIBRARY)
   get_property(type TARGET ${TARGET_LIBRARY} PROPERTY TYPE)
   if(NOT ${type} STREQUAL "STATIC_LIBRARY"
       AND NOT ${type} STREQUAL "SHARED_LIBRARY"
+      AND NOT ${type} STREQUAL "OBJECT_LIBRARY"
       AND NOT ${type} STREQUAL "MODULE_LIBRARY")
     message(WARNING "This macro can only be used with libraries")
     return()