pub fn enabled_on(&self, platform_spec: &PlatformSpec) -> EnabledTernary {
        match (self, platform_spec) {
            (PlatformStatus::Always, _) => EnabledTernary::Enabled,
            (PlatformStatus::Never, _) => EnabledTernary::Disabled,
            (PlatformStatus::PlatformDependent { .. }, PlatformSpec::Any) => {
                EnabledTernary::Enabled
            }
            (PlatformStatus::PlatformDependent { eval }, PlatformSpec::Platform(platform)) => {
                eval.eval(platform)
            }
            (PlatformStatus::PlatformDependent { .. }, PlatformSpec::Always) => {
                EnabledTernary::Disabled
            }
        }
    }
Evaluates whether this dependency is enabled on the given platform spec.

Returns `Unknown` if the result was unknown, which may happen if evaluating against an
individual platform and its target features are unknown.
guppy/src/platform/platform_eval.rs