limit native compilation - how

[Colin Baxter 😺]

I want to limit native compilation to emacs' own libraries and not
include any of my own lisp files. I tried a .dir-locals.el file 

--8<---------------cut here---------------start------------->8---
((emacs-lisp-mode .
((eval: (setq no-native-compile t)))))
--8<---------------cut here---------------end--------------->8---

in the directory I want native compilation to avoid. That didn't
work. Perhaps I can't see the wood for the trees, but I don't understand
what's wrong with the .dir-locals. Can anyone help?

Thanks - Colin.