perf(cli): faster standalone executable determination

[mmastrac]

This was showing up on the flamegraph.

14:54 $ hyperfine -S none --warmup 25 '/tmp/deno run /tmp/empty.js' 'target/release/deno run /tmp/empty.js'
Benchmark 1: /tmp/deno run /tmp/empty.js
  Time (mean ± σ):      17.2 ms ±   4.7 ms    [User: 11.2 ms, System: 4.0 ms]
  Range (min … max):    15.1 ms …  72.9 ms    172 runs
 
  Warning: Statistical outliers were detected. Consider re-running this benchmark on a quiet system without any interferences from other programs. It might help to use the '--warmup' or '--prepare' options.
 
Benchmark 2: target/release/deno run /tmp/empty.js
  Time (mean ± σ):      16.7 ms ±   1.1 ms    [User: 11.1 ms, System: 4.0 ms]
  Range (min … max):    15.0 ms …  20.1 ms    189 runs
 
Summary
  'target/release/deno run /tmp/empty.js' ran
    1.03 ± 0.29 times faster than '/tmp/deno run /tmp/empty.js'
✔ ~/Documents/github/deno/deno [faster_extract|…5⚑ 23]