add real vsync test for screen synchronization

[Frank-Buss]

This adds real VSYNC test from the graphics card instead of using the timer, because the timer is not in sync and causes a tearing effect. I also added a build script for Linux and a test script for running it with qemu. The game crashes in qemu after a few seconds, but otherwise it runs smoothly.

Video of it running on Linux in qemu:

2025-10-03.22-58-58.mp4

[jonathand-cf]

its becouse qemu runs on 1 cpu, QEMU must expose more than 1 vCPU to run correctly

[Frank-Buss]

No, this wasn't the problem. If there is only 1 core, it doesn't use the upscaling functionality. The problem was the missing RDRAND instruction. I changed the run script, works now with qemu.

[jonathand-cf]

It runs fine on my mac with

qemu-system-x86_64 \
  -machine q35,accel=tcg \
  -cpu max -smp 4 -m 1024 \
  -drive if=pflash,unit=0,format=raw,readonly=on,file="$QEMU_SHARE/edk2-x86_64-code.fd" \
  -drive if=pflash,unit=1,format=raw,file=OVMF_VARS.fd \
  -drive if=ide,media=disk,format=raw,file=fat:rw:$HOME/efidisk \
  -serial stdio

[Frank-Buss]

Yes, "-cpu max" includes the RDRAND feature.