def __init__(self, src_dir: str | Path, environment: BaseEnvironment) -> None:
        """If isolated is True(default), the builder will set up a *clean* environment.
        Otherwise, the environment of the host Python will be used.
        """
        self._env = environment
        self.executable = self._env.interpreter.executable.as_posix()
        self.src_dir = src_dir
        self.isolated = environment.project.core.state.build_isolation
        self.config_settings = environment.project.core.state.config_settings
        mode = "Isolated" if self.isolated else "Non-isolated"
        logger.info("Preparing environment(%s mode) for PEP 517 build...", mode)
        try:
            with open(os.path.join(src_dir, "pyproject.toml"), "rb") as f:
                spec = tomllib.load(f)
        except FileNotFoundError:
            spec = {}
        except Exception as e:
            raise BuildError(e) from e
        build_system = spec.get("build-system", self.DEFAULT_BACKEND)

        if "build-backend" not in build_system:
            build_system["build-backend"] = self.DEFAULT_BACKEND["build-backend"]

        if "requires" not in build_system:
            raise BuildError("Missing 'build-system.requires' in pyproject.toml")

        self.init_build_system(build_system)
If isolated is True(default), the builder will set up a *clean* environment.
        Otherwise, the environment of the host Python will be used.
        
src/pdm/builders/base.py