Why pip install -e . takes a long time?

[LukeLIN-web]

I am trying to install a CPP and python mixed project with editable mode. I am using: pip install --no-index -U -e .
https://github.com/quiver-team/torch-quiver/blob/main/setup.py
However, when I modify and rebuild the system, I use pip install --no-index -U -e . again.
CPP compile method is

from torch.utils import cpp_extension
...
setup(
...
    ext_modules=[
        cpp_extension.CppExtension()
    ],
...
)

But it takes 4 minutes, make should not take such a long time.
May you have some ideas?
Thank you for your help!