subr/build_init.subr: touch ${DEFAULT_BUILD_LOG_FNAME} and set ${BUILD_IS_PARENT=1}.
subr/ex_pkg_dispatch.subr:exp_pkg_dispatch(): set ${BUILD_IS_PARENT=0} within child process context.
subr/ex_rtl_log.subr:exp_rtl_log_printf(): append message sans attributes to ${DEFAULT_BUILD_LOG_FNAME} given ${BUILD_IS_PARENT}.