scx_utils: specify libbpf-sys to 1.4.6, bump libbpf-rs versions

[etsal]

The libbpf-sys package for the Rust schedulers has buggy behavior for versions 1.4.1 and 1.5.0: 1.4.1 crashes when linking multiple BPF objects, while using 1.5.0 causes all Rust schedulers to crash (#1074 #1015). Pin libbpf-sys 1.4.6 to avoid either problem. To use 1.4.6, also update libbbpf-rs to the most recent version.

[likewhatevs]

I kind of think we should set all instances of libbpf-rs, libbpf-sys and libbpf-cargo to the same version everywhere.

That being said, I tried doing exactly that (using 1.4.6 iirc) and 1.5.0 was still being pulled in somehow during cargo install (which is like cargo build without a Cargo.lock) despite 1.5.0 being absent from cargo-tree so idk...

[etsal]

Did you try libbpf-sys = '1.4.6', or libbpf-sys = '=1.4.6'? If it was the latter then it's very weird, it's supposed to be pinning the semantic version. The former is just a preferred version so Cargo is allowed to pull a more recent one.

[likewhatevs]

Did you try libbpf-sys = '1.4.6', or libbpf-sys = '=1.4.6'? If it was the latter then it's very weird, it's supposed to be pinning the semantic version. The former is just a preferred version so Cargo is allowed to pull a more recent one.

the latter, after seeing that not work I just added cargo install --locked to the readme instead of trying to get cargo install without --locked to work.