[2noise/ChatTTS]安装 flash-attn 可选项的时候报错

我是 Windows 10 的系统，有 NIVIDIA 显卡，命令行日志如下：

PS C:\ChatTTS> pip install flash-attn --no-build-isolation
Defaulting to user installation because normal site-packages is not writeable
Collecting flash-attn
  Using cached flash_attn-2.6.1.tar.gz (2.6 MB)
  Preparing metadata (setup.py) ... error
  error: subprocess-exited-with-error

  × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> [22 lines of output]
      fatal: not a git repository (or any of the parent directories): .git
      C:\Users\ROG\AppData\Local\Temp\pip-install-b32gjsjx\flash-attn_2297bac9ebd4415595ad37c7d00fd795\setup.py:78: UserWarning: flash_attn was requested, but nvcc was not found.  Are you sure your environment has nvcc available?  If you're installing within a container from https://hub.docker.com/r/pytorch/pytorch, only images whose names contain 'devel' will provide nvcc.
        warnings.warn(
      Traceback (most recent call last):
        File "<string>", line 2, in <module>
        File "<pip-setuptools-caller>", line 34, in <module>
        File "C:\Users\ROG\AppData\Local\Temp\pip-install-b32gjsjx\flash-attn_2297bac9ebd4415595ad37c7d00fd795\setup.py", line 134, in <module>
          CUDAExtension(
        File "C:\Users\ROG\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.12_qbz5n2kfra8p0\LocalCache\local-packages\Python312\site-packages\torch\utils\cpp_extension.py", line 1077, in CUDAExtension
          library_dirs += library_paths(cuda=True)
                          ^^^^^^^^^^^^^^^^^^^^^^^^
        File "C:\Users\ROG\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.12_qbz5n2kfra8p0\LocalCache\local-packages\Python312\site-packages\torch\utils\cpp_extension.py", line 1211, in library_paths
          paths.append(_join_cuda_home(lib_dir))
                       ^^^^^^^^^^^^^^^^^^^^^^^^
        File "C:\Users\ROG\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.12_qbz5n2kfra8p0\LocalCache\local-packages\Python312\site-packages\torch\utils\cpp_extension.py", line 2419, in _join_cuda_home
          raise OSError('CUDA_HOME environment variable is not set. '
      OSError: CUDA_HOME environment variable is not set. Please set it to your CUDA install root.

      torch.__version__  = 2.3.1+cpu

      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> See above for output.

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.

这个 CUDA_HOME 环境变量该怎么设置呀？