<!--
Please provide a description of your change below this comment.

Then please complete the checklist.

Useful contribution guidelines and tips are in docs/developers.md.

Warning: please make sure that you have implemented and tested your
         change against the latest version of bpftrace (unless opening a
         PR for a release branch).
-->

##### Checklist

- [ ] Language changes are updated in `docs/language.md`, `docs/stdlib.md`, or `man/adoc/bpftrace.adoc`
- [ ] User-visible and non-trivial changes updated in `CHANGELOG.md`
- [ ] The new behaviour is covered by tests
