fix UTF-8 cli args to exec

[jhheider]

We need the actual buffer size, instead of string length. Slower, but otherwise we risk truncating input.

Example of failure in action: https://github.com/teaxyz/pantry/actions/runs/5506185252/jobs/10042047292

stage.ts is copying from a non-existent unpack directory, resulting in no source. see also the tarball ending in tar.g.

[what-the-diff]

PR Summary

• Improved String Length Calculation
  The method for determining the length of strings in our software has been enhanced. Previously, the program was just counting the number of characters, but now it's looking at the entire encoded length of the string. This change will improve string handling especially when dealing with complex characters.

• Additional Test for UTF-8 Argument Handling
  We've added a new test into the software's suite to verify that specific coding language constructs (shebangs in this case) can properly handle arguments in UTF-8 format. This new check will ensure our handling of diverse character sets remains robust. The test executes a sample script, then verifies that the output matches what we're expecting.