package not found when pdm build

[abersheeran]

• I have searched the issue tracker and believe that this is not a duplicate.

Make sure you run commands with -v flag before pasting the output.

Steps to reproduce

Clone https://github.com/abersheeran/baize/tree/use-pdm

pdm install -dG build
pdm build

Actual behavior

import mypyc get ImportError.

Expected behavior

Compile some .py files to .pyd/.so

Environment Information

# Paste the output of `pdm info && pdm info --env` below:
PDM version:        1.8.2
Python Interpreter: C:/Users/aber/AppData/Local/Programs/Python/Python39/python.exe (3.9)
Project Root:       C:/Users/aber/Documents/GitHub/baize
Project Packages:   C:\Users\aber\Documents\GitHub\baize\__pypackages__\3.9
{
  "implementation_name": "cpython",
  "implementation_version": "3.9.6",
  "os_name": "nt",
  "platform_machine": "AMD64",
  "platform_release": "10",
  "platform_system": "Windows",
  "platform_version": "10.0.19043",
  "python_full_version": "3.9.6",
  "platform_python_implementation": "CPython",
  "python_version": "3.9",
  "sys_platform": "win32"
}

[frostming]

Add --no-isolation option in #635