Incompatible ABI when building shared libs with cmake vs autotools

[antonio-rojas]

What version of protobuf and what language are you using?
Version: 21.2
Language: C++

What operating system (Linux, Windows, ...) and version?
Linux

What runtime / compiler are you using (e.g., python version or gcc version)
GCC 12

What did you do?
Compiling shared libraries with autotools doesn't define PROTOBUF_USE_DLLS. Therefore, in
https://github.com/protocolbuffers/protobuf/blob/main/src/google/protobuf/arena.cc#L223
the compiled shared library exports the ThreadSafeArena::thread_cache_ symbol.

On the other hand, compiling then with cmake defines PROTOBUF_USE_DLLS so the symbol ThreadSafeArena::thread_cache() is exported instead in
https://github.com/protocolbuffers/protobuf/blob/main/src/google/protobuf/arena.cc#L217,
which makes the ABI different depending on the build system used.

[fowles]

Protobuf does not support heterogenous build modes like this. Medium term we plan on removing autotools support entirely