legba fails to build with OpenSSL 4.0

Versions:

- legba HEAD https://github.com/evilsocket/legba/commit/c82104a4f03d7b050bea2a6d255b0e5ff5947436
- OpenSSL 4.0.0

Steps to reproduce:
```
$ git clone https://github.com/evilsocket/legba.git
$ cd legba
$ OPENSSL_NO_VENDOR=true cargo build
....
--- stderr

thread 'main' (5826) panicked at /build/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/openssl-sys-0.9.109/build/main.rs:492:5:

This crate is only compatible with OpenSSL (version 1.0.1 through 1.1.1, or 3), or LibreSSL 2.5
through 4.1.x, but a different version of OpenSSL was found. The build is now aborting
due to this version mismatch.

note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```
- [legba-openssl-4.0-build-failure.log](https://github.com/user-attachments/files/30362581/legba-openssl-4.0-build-failure.log)
- [openssl-sys 0.9.114](https://github.com/rust-openssl/rust-openssl/compare/openssl-sys-v0.9.113...openssl-sys-v0.9.114)
- [openssl 0.10.78](https://github.com/rust-openssl/rust-openssl/compare/openssl-v0.10.77...openssl-v0.10.78)

@kpcyrd @pierres

Start by reproducing the failure with `OPENSSL_NO_VENDOR=true cargo build` against OpenSSL 4.0.0, then inspect the linked `openssl-sys 0.9.114` and `openssl 0.10.78` changes as the relevant dependency entry points. Done means legba builds successfully with OpenSSL 4.0.0 without the version-mismatch panic.

Written by the indexing model from the issue text.