https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120106
--- Comment #17 from Eric Botcazou <ebotcazou at gcc dot gnu.org> --- > I agree, but the top level Makefile does export _BUILD settings to sub-Makes > via environment variables, not on the Make command line. My understanding is that it does so when configuring sub-directories only; for sub-makes, it should pass the flags on the command line.
