Good point.

:) thats why its on every checklist :)

Was that the wrong way to do it?

Nope, but it doesn't compile the c header it merely parses so there are https://metacpan.org/pod/h2ph#BUGS ... its old :)

And is it normal that I have to do that on my own (as I said I installed via perlbrew and there were no .phs generated then?

Yes, absolutely, h2ph just doesn't happen when building perl ... IIRC it didn't even as far back as 5.6.1

The alternatives seem to be h2ph h2xs ExtUtils::Constant C::Scan::Constants ExtUtils::H2PM

I like the ones that use a compiler to get the real number ...