cargo flamegraph should set cargo environment variables

[kuviman]

When using cargo run normally, cargo sets environment variables that can be detected from the binary

https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-crates

Would be nice if running via cargo flamegraph would do same

[djc]

Sure, would you be able to submit a PR?

[kuviman]

I probably would be able, yes

I was wondering though if this is actually wanted. I dont know if people are using those variables from the binary and not during compilation, my use case might be too specific and i can easily work without this

[djc]

Yeah, I do think those variables are mainly intended for compilation time. Since flamegraph doesn't try to compile (it only reuses the Cargo metadata to find compilation targets IIRC), I don't think it would really apply here?