Remove unused code warnings from Windows build

Author: AJIOB

src/dist/pkg.rs

@@ -20,6 +20,7 @@ use std::str;
 
 use crate::errors::*;
 
+#[cfg(all(target_os = "linux", target_arch = "x86_64"))]
 pub use self::toolchain_imp::*;
 
 pub trait ToolchainPackager: Send {