How to use dGPU in Optimus systems via Rust

main.rs

#![feature(link_args)]

// Don't try and do this via cargo it's a huge disaster,
// just ignore the ominous warnings about link_args being
// broken. (requires nightly, too, hurray)
#[cfg(target_os="windows")]
#[link_args="/EXPORT:NvOptimusEnablement"]
extern {}

#[allow(non_upper_case_globals)]
#[no_mangle]
pub static NvOptimusEnablement: u32 = 1;