The import script as is is broken. In particular there are errors when running make dist:

make[3]: Entering directory '/tmp/import-libunwind.mWTo1K/doc'
make[3]: *** No rule to make target 'distdir'.  Stop.

make dist is also broken on upstream libunwind, and there are upstream cmake rather than make files, though make is still referenced in documentation. It's possible that our import script hasn't worked for quite a while, and we're just now documenting it.

We should fix the script so that it will be easier to directly pull from the fork instead of porting over particular commits. At the moment, we must cherry-pick individual commits to the unwind folder on the mongo repo.