Bump external/libbtf from 0a4ef1f to 3c2012b

Bumps [external/libbtf](https://github.com/Alan-Jowett/libbtf) from `0a4ef1f` to `3c2012b`.
- [Release notes](https://github.com/Alan-Jowett/libbtf/releases)
- [Commits](Alan-Jowett/libbtf@0a4ef1f...3c2012b)

---
updated-dependencies:
- dependency-name: external/libbtf
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>