Resolves clippy errors (#128)

src/steps/os/archlinux.rs

@@ -245,7 +245,7 @@ impl Aura {
 
 impl ArchPackageManager for Aura {
     fn upgrade(&self, ctx: &ExecutionContext) -> Result<()> {
-        let sudo = which("sudo").unwrap_or(PathBuf::new());
+        let sudo = which("sudo").unwrap_or_else(PathBuf::new);
         let mut aur_update = ctx.run_type().execute(&sudo);
 
         if sudo.ends_with("sudo") {