Reproducer for a Metal bug affecting comparison

See shader.metal for the MSL code, along with comments about alternatives that both do and do not exhibit the problem.

Reproduced on:

 macOS: Sonoma 14.1
 Model Name: MacBook Pro
 Chip: Apple M1 Pro

Does not reproduce on Intel or AMD GPUs running macOS 14.1.

make
./metal-comparison-bug

This should produce:

output = 0

But on Apple M1 running macOS 14.1 instead produces:

output = -992

Name		Name	Last commit message	Last commit date
Latest commit History 1 Commit
.gitignore		.gitignore
Makefile		Makefile
README.md		README.md
main.m		main.m
shader.metal		shader.metal