verify_rust_std: fix rustc arguments passing

   Compiling core v0.0.0 (/home/runner/work/distributed-verification/distributed-verification/verify-rust-std/library/core)
error: multiple input filenames provided (first two filenames are `core` and `/home/runner/work/distributed-verification/distributed-verification/verify-rust-std/library/core/src/lib.rs`)

Author: zjp-CN

src/bin/verify_rust_std/main.rs

@@ -36,7 +36,7 @@ fn main() -> Result<()> {
                 "rustc": format!("rustc {}", args.join(" "))
             });
             ENV.write_rustflags_json(&json)?;
-            build_core(args.split_off(1))
+            build_core(args)
         } else {
             // build non-core crates
             run("rustc", &args, &[])