add custom target to remove/reset collected coverage data

        add_custom_target(clean_coverage_html

        add_custom_target(clean_coverage_html

            ${CMAKE_COMMAND} -E remove_directory ${COVERAGE_HTML_DIR}

            ${CMAKE_COMMAND} -E remove_directory ${COVERAGE_HTML_DIR}

        )

        )

       add_custom_target(reset_coverage

            ${CMAKE_COMMAND} -E remove -f */*.gcda */*/*.gcda */*/*/*.gcda

                              */*/*/*/*.gcda */*/*/*/*/*.gcda */*/*/*/*/*/*.gcda

                              */*/*/*/*/*/*/*.gcda */*/*/*/*/*/*/*/*.gcda

                              */*/*/*/*/*/*/*/*/*.gcda */*/*/*/*/*/*/*/*/*/*.gcda

            WORKIND_DIRECTORY ${CMAKE_BINARY_DIR}

            COMMENT "Deleting coverage report data files"

       )

    endif()

    endif()

endif()

endif()