Would it be worth adding a tty.warning somewhere in CMakePackage if build_type is set, there are compiler flags, and the flag handler uses the build system? If a package overrides build_type and sets their own default, they may be confused why the flags suddenly aren't set. IMO flags_to_build_system_args would be an appropriate place.

@scheibelp if we were to do that we would need to do it for all flag handlers, the bad behavior appears under all flag_handlers, it's about setting incompatible flags, in whatever way they are set.

I don't think we would want to set that warning from the build environment, because then it would be written to the build log not the terminal. I'm not sure where before that we could set it though, without seeing it every time we concretize a spec, which I think would be overkill. I don't think it's a bad idea, but I'm not sure where we could reasonably set that message.

Closing as stale (similarly to the recently closed #5265)