Autoconf and m4

Yes, I've found that explicit requests for things like that are best. It's really frustrating when you copy a configure line from one machine to another and get a result because somewhere in the middle of the log dependency X's state differed between the two machines and you're left figuring out why behavior Y differs. *Some* things make sense to just inspect and change, but that's for things that you can polyfill (BSD routines on Linux or glibc routines elsewhere) or are just plain impossible on the platform (e.g., v4l support on macOS or Windows).