message: Don't define pugixml import target if it already exists
  This fixes duplicate target definition errors when find_package(pugixml)
  is called twice in a build.
  Fixes
diff: @@ -5,7 +5,7 @@ include("${CMAKE_CURRENT_LIST_DIR}/pugixml-targets.cmake")
  # If the user is not requiring 1.11 (either by explicitly requesting an older
  # version or not requesting one at all), provide the old imported target name
  # for compatibility.
  -if (NOT DEFINED PACKAGE_FIND_VERSION OR PACKAGE_FIND_VERSION VERSION_LESS "1.11")
  +if (NOT TARGET pugixml AND (NOT DEFINED PACKAGE_FIND_VERSION OR PACKAGE_FIND_VERSION VERSION_LESS "1.11"))
  add_library(pugixml INTERFACE IMPORTED)
  # Equivalent to target_link_libraries INTERFACE, but compatible with CMake 3.10
  set_target_properties(pugixml PROPERTIES INTERFACE_LINK_LIBRARIES pugixml::pugixml)
  