Well, I am officially giving up on trying to set up a bare metal development environment for the Teensy 4.0, at least for now. I believe it is possible, but I'd rather not fight against the platform too hard. If I gave it some more time, I could probably reasonably set up and use NXP's MCUXpresso, but just using GNU Arm and Makefiles seems extra challenging.
As much as I hate the Arduino IDE, if it works, it works, and it's the path of least resistance.
@Ricardus @twylo I don't dislike the Arduino IDE; however, it is somewhat disturbing whenever I read about any kind of so-called "embedded" environment where any competent developer is unable to establish a bare-metal development environment in a reasonable period of time. In my mind, such environments are correspondingly *not* embedded.
I'm sorry you are running into problems; however, regardless of which approach you take, I'm eager to stay abreast of your developments!
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko