Implement ci target for Makefile to reproduce github CI actions & artifacts

[ia]

• Please check if the PR fulfills these requirements

• The changes have been tested locally
• There are no breaking changes

• What kind of change does this PR introduce?
  Implement ci target for Makefile to reproduce github CI actions & artifacts.

• What is the current behavior?
  There is no fast & easy way to reproduce github CI jobs locally, for testing & debugging purposes or for preparing local zips with builds in bulk.

• What is the new behavior (if this is a feature change)?
  By running one make ci command, the produced binaries will be collected and packed into zips inside local BUILDS/CI directory with the same content as downloadable zips from Actions tab on github has.

• Other information:
  Unfortunately, that's not "reproducible builds" per se, but nevertheless it's useful to have the same pipeline locally to exclude the factor of build environment in the case of some problem.

P.S. After a bit of puzzling myself how to take into consideration all the variations with names & lang options related to metadata json generating/parsing inside of Makefile, I just took some liberty to tweak a bit metadata.py instead. ;)

[Ralim]

🤞🏼 the comments make sense

[ia]

🤞🏼 the comments make sense

Sure! Since this change in metadata.py is for very specific use case, I tried to be as less "invasive" to existing code base as possible, hence some shortcuts have been implied.

At first I wondered why the script scans all the files in the directory instead of reduce scanning to a pattern since the script have knowledge about model including multilang status (the first argument for json output file name) but:

• I'm not sure I could do better myself;
• my policy [for any project] is: if you don't know for 100% sure why some design decisions have been made long before you - don't touch it (or keep it fully compatible even after refactoring) because if you do you probably will break something somewhere.

[ia]

Oh, wait... since we change this script & a bit of its logic anyway, I think I have just one more little idea for tiny improvement here...

[ia]

Done & tested: I made a full local build using make ci and then I did compare content of metadata.zip with the one from github: everything seems fine. The only one thing which doesn't match between local & github json files is a commit tag but that's another matter which I was going to work on anyway soon.