[P2] Linux source builds fail when git clean runs outside the dependency checkout

[drebbe-intrepid]

Bug

_build_libicsneo_linux runs git clean -xdf with cwd="libicsneo", although the cloned Git repository is at libicsneo//source. In an extracted source distribution there is no parent .git either, so the build fails before CMake.

Reviewed commit: 45167e09de6b886cd451a4245f842c8221349711 (current master on 2026-09-15).
Source: build_libicsneo.py:126

Reproduction

Create an extracted-source-style directory outside any Git checkout, with the dependency repository nested under libicsneo/0dd8dbf/source. Invoke _build_libicsneo_linux() from that directory. A focused reproduction (no downloads or hardware):

import importlib.util, os, pathlib, subprocess, tempfile
source = pathlib.Path('build_libicsneo.py').resolve()
root = pathlib.Path(tempfile.mkdtemp())
dependency = root/'libicsneo'/'0dd8dbf'/'source'
dependency.mkdir(parents=True)
subprocess.run(['git', 'init', '--quiet', str(dependency)], check=True)
os.chdir(root)
spec = importlib.util.spec_from_file_location('review_build', source)
module = importlib.util.module_from_spec(spec)
spec.loader.exec_module(module)
module._build_libicsneo_linux()

Observed / expected

The first command fails with exit 128: fatal: not a git repository (or any of the parent directories): .git. This focused Git-path reproduction was run on Windows; the Python command and Git repository-discovery behavior are the same in the Linux build path. A complete Linux source build was not run. Expected builds from source archives to work without a .git directory for python_ics itself.

Suggested fix and regression coverage

Clean only the intended dependency build directory, or run Git operations in LIBICSNEO_SOURCE if source cleaning is actually needed. Use the existing LIBICSNEO_BUILD path consistently. Add a Linux build check from an unpacked sdist with no parent .git.

Validation environment

Windows x64, CPython 3.14.5, extension rebuilt from the commit above. Hardware-dependent entry points below were exercised with a mock DLL, not a connected device. The existing 30 tests pass despite these findings.