feat: prevent linking when LLVM bytecode version isn't the one expected by the linker

[qjerome]

It would be very nice to have bpf-linker raising an error when an attempt to link against incompatible bytecode is made.
This could prevent future issues like #318

[vadorovsky]

This would've been easy to implement if LLVM C API was exposing BitcodeReader::getBitcodeProducerString from C++ API, but unfortunately it doesn't.

I've managed to vibe code this solution with manual bitcode parsing: vadorovsky@f776b03. It surprisingly works and does the job with detection correctly. But I'm feeling uneasy with actually putting that into the linker. I'll try to clean that up and see if I can get it to something mergeable.

[vadorovsky]

Submitted llvm/llvm-project#166063 BTW