Update build args and find program for API changes

[mattnite]

This does change the usage of hello client subcommand. Before we had an assumption that if only one arg was passedd in, you'd default to the hello server. If you passed more than one in, the second argument is expected to be a path to the server binary.

With the changes to Zig master, we can only pass through the args on the commandline, not inspect them. I've worked around this behavior by passing in the server binary explicitly using a named option over an arg positional.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.94%. Comparing base (b886a2b) to head (b868680).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #38   +/-   ##
=======================================
  Coverage   98.94%   98.94%           
=======================================
  Files           3        3           
  Lines        1514     1515    +1     
=======================================
+ Hits         1498     1499    +1     
  Misses         16       16           

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[Techatrix]

The setup of the hello client example is a bit messy which I was planning to rework anyway so this should be fine.

The banner in the install steps on the README should be updated to this:

> [!NOTE]
> The default branch requires Zig `0.17.0-dev.601+0ff175b69` or later. Checkout the `0.16.x` branch when using Zig 0.16

I will take care of creating the 0.16.x branch.