demo: Disable compiler optimization

[RobLoach]

Using -O2 across the demos enables some optimization, which is great, but results in slow compilation. This can be particularly slow when testing out some new components during development. I recommend diabling this to speed up compilation when testing.

[awschult002]

if you havent heard of the "Tiny C Compiler" I cannot recommend it enough. Its the fastest compiler out there and its absolutely perfect for super quick development testing. I would not recommend it for release because its non-optimizing; but I use it all of the time for testing and its lightning fast.

https://github.com/TinyCC/tinycc

i am not recommending that the project call out this compiler, because the project uses the environment variable for that, which is preferred. I just have my env var setup to use tcc. works great

[RobLoach]

Glad switching the CC environment variable worked well, and happy to hear that tinycc compiles it fine 👍

Updated the PR.

[riri]

I just made a quick clone and try on sdl and x11 demos, I think it's trivial enough to merge without further tests