message: Add POSITION_INDEPENDENT_CODE option
  Allow to use the static library in other dynamic librairies. This is a standard cmake option
diff: @@ -85,6 +85,7 @@ set_target_properties(pugixml-shared pugixml-static pugixml
  PROPERTIES
  MSVC_RUNTIME_LIBRARY ${CMAKE_MSVC_RUNTIME_LIBRARY}
  EXCLUDE_FROM_ALL ON
  + POSITION_INDEPENDENT_CODE ON
  SOVERSION ${PROJECT_VERSION_MAJOR}
  VERSION ${PROJECT_VERSION})
  