Cargo: same files; multiple builds with different envs

Say we have a project called test. test has a codebase with a large amount of conditional compilation in it. I need to build multiple versions of test - each one with a different output name, and different cfg options enabled.

Currently, I can almost get what I want with the following snippet for a Cargo.toml:

[[bin]]
name = "run"
path = "src/main.rs"

[[bin]]
name = "run_d"
path = "src/main.rs"

However, both of the output binaries are identical. What I need is some way to specify different cfg arguments for each build - like the --cfg my_custom_val argument to rustc.

Is this possible? And if so, how?

Disclaimer: quite new to rust, it's highly likely I overlooked something - not used to rust/cargo's build system.