I just took a look at the easyblock, and it does seem a bit of overkill, although one could argue about that.

Easyblocks are there to implement aspects of build procedures in code once, and then forget about it. If you need to remember to add some lines in an easyconfig file because otherwise the build doesn't work, then put it in an easyblock instead (however small the module ends up to be).

This is kind of a corner case, since the Libint2 build itself works fine without this easyblock, and the problem only pops up when Libint2 is a dependency to something else.

So for now, I'd agree with you this is overkill. The alternative is to add the following line to all Libint2 easyconfig files:

modextrapaths = {'CPATH': "include/libint2"}

Downside of this: if it's forgotten in one libint2 easyconfig that is used as a dep for something that really requires this, the build won't work, and you might be left wondering why and refiguring things out all over again.

With an easyblock in place that only has this today, you can simply forget about this, as EasyBuild will make sure the job is always done (even if the line is missing in the easyconfig file).

And also, who knows, maybe more stuff will be added in the EB_Libint2 easyblock later on?
You can add the custom sanity check in the easyblock, and thus get rid of it in the easyconfig file, and maybe also the custom configopts that are used in the libint2 easyconfigs in easybuilders/easybuild-easyconfigs#381. Once you have an easyblock, you might as well put it to good use.

That being said: up to you.

Good. I'll try to add in some extra's.

This may in the long run become a heavier easyblock because the libint2 library source code is generated by the libint2 program. Hence there are many different libint2 flavors with a rather non-standard build process. For now, I just picked the flavor I need, which can also be downloaded from sourceforge (instead of having to generate it).

OK, sounds great. Do post another remark when you feel you're done (we don't get notifications for additional commits that are added).

This should be fine now, unless there are other comments.

It is fine now, tested in the process of testing all easyconfigs touched in easybuilders/easybuild-easyconfigs#385, so good to merge in!

Thanks @tovrstra, great job. 👍