dnl figure out whether we need to build Tk
build_brlcad_tk="no (using system)"
if test "x$bc_build_tk" != "xno" ; then
    build_brlcad_tk=yes
else
    if test "x$bc_build_tk" = "xno" ; then
        if test "x$tk_works" = "xno" ; then
            AC_MSG_NOTICE([libtk was disabled, but no system Tk library was foun
            BC_RETRY_CONFIGURE([$this], [$args])
            AC_MSG_NOTICE([}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}])
            AC_MSG_NOTICE([Try adding --enable-tk-build])
            AC_MSG_ERROR([*** Tk was disabled, yet no usable libtk system librar
        fi
    else
        dnl automatic detection
        if test "x$tk_works" = "xno" ; then
            build_brlcad_tk=yes
        fi
    fi
fi
AC_MSG_CHECKING(whether to build Tk)