bpf-linker is not compatbile with -fuse-ld

[addisoncrump]

I encountered this while trying to run aya-rs/aya#916 locally.

warning: [email protected]:   = note: ... "-fuse-ld=mold"
warning: [email protected]:   = note: error: unexpected argument '-f' found
warning: [email protected]:           
warning: [email protected]:             tip: to pass '-f' as a value, use '-- -f'
warning: [email protected]:           
warning: [email protected]:           Usage: bpf-linker [OPTIONS] --output <OUTPUT> [INPUTS]...
warning: [email protected]:           
warning: [email protected]:           For more information, try '--help'.

This is because I use the mold linker locally in my cargo.toml:

[target.x86_64-unknown-linux-gnu]
rustflags = [
    "-C", "link-arg=-fuse-ld=mold",
]

Confusingly, I only have this set for when the target is x86_64. Is this another bug?

[tamird]

That's a cargo-in-cargo bug indeed. RUSTFLAGS has a very high priority, so it ends up winning out over the linker specified in the integration-ebpf crate. Can you use linker = "mold" instead?