workaround for ejabberd-22.05 to build with erlang 21

[wertziop]

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rebar and reabar3 provided by ejabberd-22.05 are build against erlang 22 and not runnable on older erlang versions. I just tried this quick fix by myself.

Maybe someone could review my proposal. My language skills are limited, both english and reST :)

(Maybe a better solution is to update erlang/OTP?)

[noave]

If the guide is currently not working for the newest ejabberd version and this fixes it, you don't need to add it just as a note but may rework the whole guide for the newest version

[noave]

Erlang has been updated recently https://manual.uberspace.de/changelog/#v7-14-short

Would you like to check the guide again with this and and make it working?

[coderkun]

ejabberd 22.10 works fine with Erlang 24. I can test to compile it with Erlang 25.

[wertziop]

sorry, didn‘t found enough time to review my pull request. please ignore it!

I followed you documentation again and everything is perfectly fine - if you switch erlang/OTP to a version above 22. when i wrote the work around, i didn‘t know about switching language versions with standard uberspace tools.

sorry again!

[hasmaneuroda]

I think it should be mentioned that you can switch language versions by using uberspace tools version use erlang 25 as it's crucial to use a version > 21, like wertziop already wrote.