Cleanup code

Co-authored-by: Aleksey Kladov <aleksey.kladov@gmail.com>

cargo-miri/bin.rs

@@ -257,8 +257,7 @@ fn setup(subcommand: MiriCommand) {
 
     // Determine where the rust sources are located.  `XARGO_RUST_SRC` env var trumps everything.
     let rust_src = match std::env::var_os("XARGO_RUST_SRC") {
-        Some(val) => {
-            let path = PathBuf::from(val);
+        Some(path) => {
             // Make path absolute, but not via `canonicalize` (which does not work very well on Windows).
             env::current_dir().unwrap().join(path)
         }