[CMake] Added namespace ROOT:: on exported targets in binary tree.

cmake/modules/RootConfiguration.cmake

@@ -612,7 +612,7 @@ set(ROOT_BINARY_DIR ${CMAKE_BINARY_DIR}/bin)
 set(ROOT_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake/modules")
 
 get_property(exported_targets GLOBAL PROPERTY ROOT_EXPORTED_TARGETS)
-export(TARGETS ${exported_targets} FILE ${PROJECT_BINARY_DIR}/ROOTConfig-targets.cmake)
+export(TARGETS ${exported_targets} NAMESPACE ROOT:: FILE ${PROJECT_BINARY_DIR}/ROOTConfig-targets.cmake)
 configure_file(${CMAKE_SOURCE_DIR}/cmake/scripts/ROOTConfig.cmake.in
                ${CMAKE_BINARY_DIR}/ROOTConfig.cmake @ONLY NEWLINE_STYLE UNIX)
 configure_file(${CMAKE_SOURCE_DIR}/cmake/scripts/RootUseFile.cmake.in