Add a section in INSTALL.md to detail how to produce a released package

[ycollet]

I was trying to reproduce the package you ship on github and was not able to do so. Can you add some notes in INSTALL.md to explain how to do this ? For example, it doesn't seems to exist a rule to produce the env directory. On Windows, the dll are stored in the bin and not in the redist directory.

[AlexVeprev]

Hi @ycollet, packages from Releases page are built using internal scripts, so they can't be easily recreated from public source code. Could you please clarify the use case where you need this?

[isaevil]

@ycollet is this issue still relevant for you? Could you please respond?

[ycollet]

I just wanted to produce an installation which reproduced the same kind of directory structure and has the same files, for internal use. The installation produced by make install is useful on my side. If it's not easy to explain the differences, you can close the ticket :)

[isaevil]

Our release packages are built with internal and non-trivial way so it can't be put publicly documented. I would kindly suggest you to do that manually.