[Bug] RuntimeRrror: Ninja is required to load c++ extensions

[Flynn-Zh]

Checklist

• 1. I have searched related issues but cannot get the expected help.
• 2. The bug has not been fixed in the latest version.
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Describe the bug

use pip install sglang[all], when i run "python3 -m sglang.launch_server ...", An error occurred: "RuntimeRrror: Ninja is required to load c++ extensions"
the sglang is v0.4.0.post1，and the v0.4.0 has same error.
run check_env found CUDA_HOME is None，is CUDA_HOME mandatory？

Reproduction

pip install "sglang[all]" --find-links https://flashinfer.ai/whl/cu121/torch2.4/flashinfer/

Environment

CUDA_HOME: None