a91e9355f1
Enable the rust profiler on rust-nightly (as an unstable feature, it's not allowed on the stable toolchain). This allows it to generate code coverage reports. https://doc.rust-lang.org/unstable-book/compiler-flags/profile.html https://crates.io/crates/grcov Reviewed by: tobik Approved by: tobik (maintainer) Differential Revision: https://reviews.freebsd.org/D24765