Add a hipify build script for PufferLib 5.0

[paralin]

Follow-up to #663 targeting 5.0. Adds one 51-line build-hip.sh that runs hipify-perl on the current sources and compiles with hipcc. Generated files stay under the existing ignored build/hip/ directory.

The script handles the remaining HIP API differences, uses RCCL, and converts GPU timer ticks using HIP's wall-clock frequency. NVML/NVTX are omitted; GPU utilization displays n/a.

Verified on an RX 7700 XT (gfx1101) with ROCm 7.2.2: CartPole with a CPU environment and FP32 training, and Breakout with a GPU environment and BF16 training. Both completed 1,048,576 training steps, saved checkpoints, and passed headless checkpoint evaluation with GPU graphs enabled.

./build-hip.sh cartpole -DPRECISION_FLOAT
./build-hip.sh breakout --cu
./build/hip/puffer train

Requires ROCm and raylib 5.5. ROCM_PATH, RAYLIB_PATH, and HIP_ARCH override their defaults.