[libafl_qemu] fix build.rs

[evanrichter]

I noticed qemu was only building on one core, so I debugged the jobs environment variable. Evidently cargo forwards CARGO_BUILD_JOBS to build.rs scripts as NUM_JOBS. Other env vars for build.rs can be found here

[evanrichter]

That reference mentions:

Note that care should be taken when interpreting this environment variable. For historical purposes this is still provided but recent versions of Cargo, for example, do not need to run make -j as it'll automatically happen. Cargo implements its own jobserver and will allow build scripts to inherit this information, so programs compatible with GNU make jobservers will already have appropriately configured parallelism.

So I tested the effect of removing -j entirely, but that was still effectively -j1. It looks like somewhere ninja is receiving -j1 as an argument

[domenukk]

Thanks!

[evanrichter]

No problem! And oh boy the "i368" typo was hard to figure out 🥲

[domenukk]

Sorry 🙈