Merge topic 'fix-export-unset'

f45c16e7 Fix export file variable pollution

Source/cmExportFileGenerator.cxx

@@ -1040,6 +1040,9 @@ void cmExportFileGenerator::GenerateExpectedTargetsCode(std::ostream& os,
         "  endif()\n"
         "endforeach()\n"
         "if(\"${_targetsDefined}\" STREQUAL \"${_expectedTargets}\")\n"
+        "  unset(_targetsDefined)\n"
+        "  unset(_targetsNotDefined)\n"
+        "  unset(_expectedTargets)\n"
         "  set(CMAKE_IMPORT_FILE_VERSION)\n"
         "  cmake_policy(POP)\n"
         "  return()\n"