pub fn set_platform(&mut self, platform_spec: impl Into<PlatformSpec>) -> &mut Self {
        let platform_spec = platform_spec.into();
        self.target_platform = platform_spec.clone();
        self.host_platform = platform_spec;
        self
    }
Sets both the target and host platforms to the provided spec.
guppy/src/graph/cargo/cargo_api.rs