[Discussion] how to model GLIBC version for conan packages

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/cc @rdeterre @bc-lee @elizagamedev

this is more generic version of https://github.com/conan-io/conan/issues/3963
related issues:
https://github.com/bincrafters/community/issues/296
https://github.com/bincrafters/community/issues/267

historically, conan didn't model glibc version, relying only on compiler version for binary compatibility checks.
this causes some issues in the past, as binaries compiled with the same compiler weren't compatible across various linux distributions.
for instance, if we compiled libraries or executables via GCC 4.8 on Ubuntu 12.04, these executables and libraries fail to run/link on CentOS 7 machines. same situation with other popular Linux distributions, like RHEL, Fedora, etc.

Start by reading issue #3963 and the linked Bincrafters issues #296 and #267 to understand the compatibility cases and prior discussion. The issue does not name a file or test; work is not ready for a first contribution until the GLIBC-version model and its expected compatibility behavior are agreed.

Written by the indexing model from the issue text.