Add missing file to build system

find_path(DATE_INCLUDE_DIR

    NAMES date/date.h

)

find_path(TZ_INCLUDE_DIR

    NAMES date/tz.h

)

find_library(TZ_LIBRARY

    NAMES tz

)

include(FindPackageHandleStandardArgs)

find_package_handle_standard_args( Date 

    DEFAULT_MSG 

    DATE_INCLUDE_DIR

    TZ_INCLUDE_DIR

    TZ_LIBRARY

)

if(Date_FOUND)

    set(DATE_INCLUDE_DIRS ${DATE_INCLUDE_DIR})

    set(TZ_INCLUDE_DIRS ${TZ_INCLUDE_DIR})

    set(TZ_LIBRARIES ${TZ_LIBRARY})

    if(NOT TARGET Date::TZ)

        add_library(Date::TZ UNKNOWN IMPORTED)

        set_target_properties(Date::TZ PROPERTIES

            IMPORTED_LOCATION "${TZ_LIBRARY}"

            INTERFACE_COMPILE_DEFINITIONS "USE_OS_TZDB=1"

            INTERFACE_INCLUDE_DIRECTORIES "${TZ_INCLUDE_DIR}"

        )

    endif()

endif()

mark_as_advanced(

    DATE_INCLUDE_DIR

    TZ_INCLUDE_DIR

    TZ_LIBRARY

)