How do I set features using spirv-builder?

[LegNeato]

I have a shader crate that has different functionality controlled by features. I need the host's build.rs (using spirv-builder) to turn features on and off when compiling the gpu code.

There doesn't seem to be an api: extra_arg() appears to be for LLVM args, and setting RUSTFLAGS in environment variables in build.rs doesn't seem to do it either.

[LegNeato]

Ok, looks like there isn't a built-in way but it respects RUSTGPU_RUSTFLAGS

std::env::set_var("RUSTGPU_RUSTFLAGS", "--cfg feature=\"whatever\"");