Allow passing additional arguments to cargo test and cargo bench in rust-script

[leemars]

Based on the information from Stack Overflow, when executing tests with cargo test, the --nocapture flag is required to display the output of println! in Rust tests. However, the current implementation of rust-script ignores all additional arguments when executing scripts with the --test flag (and likely also with the --bench mode, based on the code).

To fix this, I propose a minor change: when the build_kind is not Normal (i.e., when it's Test or Bench), we append script_args to the command line.

Although this is a small change, considering the complexity of real-world environments, I am not certain whether supporting the passing of additional arguments to cargo test, cargo bench, and the tested programs will introduce any additional security issues (hopefully not).

Welcome any feedback or suggestions for improvement.