--- a/Makefile	Tue Feb 17 17:16:27 2026 +0100
+++ b/Makefile	Tue Feb 17 17:18:10 2026 +0100
@@ -17,13 +17,13 @@
 	hg kwarchive __arch
 
 build:
-	python -m build
-	# NOTE: Postprocessing is now done by the intree build backend
-	#       in intree-build-helper/cutils_build.py.
+	python setup.py sdist bdist_wheel
+	python _postprocess-sdist.py
+	gzip --best dist/*tar
 
 distclean: clean
 # package build information
-	rm -rf dist/ *.egg-info
+	rm -rf build/ dist/ *.egg-info
 
 # Full clean build for sdist, wheel and docs
 dist: distclean build

--- a/_postprocess-sdist.py	Tue Feb 17 17:16:27 2026 +0100
+++ b/_postprocess-sdist.py	Tue Feb 17 17:18:10 2026 +0100
@@ -1,90 +1,77 @@
 # -*- coding: utf-8 -*-
 # :-
-# SPDX-FileCopyrightText: © 2025-2026 Franz Glasner
+# SPDX-FileCopyrightText: © 2025 Franz Glasner
 # SPDX-License-Identifier: BSD-3-Clause
 # :-
-"""Postprocress a .tar.gz-sdist to include tests/data with symlinks as symlinks.
+"""Postprocress a .tar-sdist to include tests/data with symlinks as symlinks.
 
 Produce an sdist with all the data in :file:`tests/data/`::
 
   rm -rf dist py_cutils.egg-info
-  python -m build
+  python setup.py sdist
   python _postprocess-sdist.py
+  gzip dist/*.tar
 
 """
 
 from __future__ import print_function, absolute_import
 
 try:
-    import tomllib
+    from configparser import ConfigParser
 except ImportError:
-    import tomli as tomllib
+    from ConfigParser import SafeConfigParser as ConfigParser
 import importlib
+import io
 import os
-import io
 import tarfile
-import gzip
 
 
 def main():
-    with open("pyproject.toml", "rb") as cfgfile:
-        cfg = tomllib.load(cfgfile)
-    project_name = cfg["project"]["name"]
-    normalized_project_name = project_name.replace("-", "_")
-    project_version = cfg["project"].get("version")
-    if project_version is None:
-        assert "version" in cfg["project"]["dynamic"]
-        project_version = cfg["tool"]["setuptools"]["dynamic"]["version"]
-        if "attr" in project_version:
-            vermodname, dummy, vermodattr = (project_version["attr"]
-                                             .strip()
-                                             .rpartition('.'))
-            assert dummy is not None and vermodattr is not None
-            vermod = importlib.import_module(vermodname)
-            project_version = getattr(vermod, vermodattr)
+    with io.open("setup.cfg", "rt", encoding="utf-8") as cfgfile:
+        cp = ConfigParser()
+        if hasattr(cp, "read_file"):
+            cp.read_file(cfgfile, "setup.cfg")
         else:
-            assert False
-    #
-    # PEP 625 requires that sdists are of the form
-    # <normalized_project_name>-<project_version>.tar.gz
+            cp.readfp(cfgfile, "setup.cfg")
+    project_name = cp.get("metadata", "name")
+    project_version = cp.get("metadata", "version")
+    if project_version.startswith("attr:"):
+        vermodname, dummy, vermodattr = (project_version[5:]
+                                         .strip()
+                                         .rpartition('.'))
+        assert dummy is not None and vermodattr is not None
+        vermod = importlib.import_module(vermodname)
+        project_version = getattr(vermod, vermodattr)
+    elif project_version.startswith("file:"):
+        assert False
     #
-    archive_name = "{}-{}.tar.gz".format(
-        normalized_project_name, project_version)
-    uncompressed_archive_name = "{}-{}.tar".format(
-        normalized_project_name, project_version)
+    # Compressed tar files cannot be modified by Python: make sure the
+    # originally generated archive is uncompressed.
+    #
+    assert cp.get("sdist", "formats") == "tar"
+
+    archive_name = "{}-{}.tar".format(project_name, project_version)
     archive_path = "dist/" + archive_name
-    uncompressed_archive_path = "dist/" + uncompressed_archive_name
     assert os.path.isfile(archive_path)
-    assert not os.path.isfile(uncompressed_archive_path)
 
     # the directory within the archive
-    archive_path_prefix = "{}-{}".format(
-        normalized_project_name, project_version)
+    archive_path_prefix = "{}-{}".format(project_name, project_version)
 
-    egg_directory = "{}.egg-info".format(normalized_project_name)
+    egg_directory = "{}.egg-info".format(project_name.replace("-", "_"))
     assert os.path.isdir(egg_directory)
     sources_txt_path = "{}/SOURCES.txt".format(egg_directory)
     sources_txt_arcname = "{}/{}/SOURCES.txt".format(
         archive_path_prefix,
         egg_directory)
 
-    # Uncompress
-    with gzip.GzipFile(filename=archive_path, mode="rb") as ca:
-        with open(uncompressed_archive_path, "wb") as uca:
-            while True:
-                data = ca.read(64*1024)
-                if not data:
-                    break
-                uca.write(data)
-
-    with tarfile.TarFile(uncompressed_archive_path, "r") as tf:
+    with tarfile.TarFile(archive_path, "r") as tf:
         sf = tf.extractfile(sources_txt_arcname)
         try:
             sources_txt = sf.read()
         finally:
             sf.close()
 
-    with tarfile.TarFile(uncompressed_archive_path, "a") as tf:
+    with tarfile.TarFile(archive_path, "a") as tf:
         arcname = "{}/tests/data".format(archive_path_prefix)
         try:
             info = tf.getmember(arcname)
@@ -126,18 +113,6 @@
         #
         tf.addfile(sources_info, sf)
 
-    # Compress
-    with open(uncompressed_archive_path, "rb") as uca:
-        with open(archive_path, "wb") as ca:
-            with gzip.GzipFile(filename=uncompressed_archive_name,
-                               fileobj=ca,
-                               mode="wb") as gzfile:
-                while True:
-                    data = uca.read(64*1024)
-                    if not data:
-                        break
-                    gzfile.write(data)
-
 
 def b(buf, encoding="ascii"):
     if isinstance(buf, bytes):

--- a/pyproject.toml	Tue Feb 17 17:16:27 2026 +0100
+++ b/pyproject.toml	Tue Feb 17 17:18:10 2026 +0100
@@ -1,66 +1,4 @@
-# Pure-Python-Build
+# Pure-Python-Build for Python2.7 and older Python3 versions
 [build-system]
-requires = ["setuptools>=77.0"]
-# This is a intree wrapper for setuptools.build_meta
-build-backend = "cutils_build"
-backend-path = ["intree-build-helper"]
-
-[project]
-name = "py-cutils"
-description = "Pure Python implementation of some coreutils with some extensions"
-#
-# NOTE: This is the *distribution* license (e.g. includes vendored stuff).
-#       There is no such thing here as a "project" license.
-#
-license = "BSD-3-Clause AND MIT"
-license-files = [
-  "LICENSES/BSD-3-Clause.txt",
-  "LICENSES/MIT.txt"
-]
-authors = [
-  {name = "Franz Glasner", email = "fzglas.hg@dom66.de"},
-]
-classifiers = [
-    "Development Status :: 5 - Production/Stable",
-    "Environment :: Console",
-    "Intended Audience :: Developers",
-    "Intended Audience :: End Users/Desktop",
-    "Intended Audience :: System Administrators",
-    "Operating System :: OS Independent",
-    "Programming Language :: Python :: 2.7",
-    "Programming Language :: Python :: 3",
-    "Topic :: System",
-    "Topic :: Utilities"
-]
-requires-python = ">=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*"
-dynamic = ["version", "readme"]
-
-[project.urls]
-homepage = "https://hg2.dom66.de/hgrepos/Python/apps/py-cutils"
-download = "https://pypi2.dom66.de/simple/py-cutils/"
-source = "https://hg2.dom66.de/hgrepos/Python/apps/py-cutils"
-
-[project.scripts]
-py-dos2unix = "cutils.dos2unix:main"
-py-genpwd = "cutils.genpwd:main"
-py-shasum = "cutils.shasum:main"
-py-treesum = "cutils.treesum:main"
-
-[tool.setuptools]
-include-package-data = false
-platforms = ["any"]
-zip-safe = true
-packages = [
-    "cutils",
-    "cutils.util",
-    "cutils.crcmod",
-    "cutils.crcmod.python2",
-    "cutils.crcmod.python3"
-]
-
-[tool.setuptools.dynamic]
-version = {attr = "cutils.__version__"}
-readme = {file = ["README.txt"], content-type = "text/x-rst"}
-
-[tool.setuptools.package-data]
-"cutils.crcmod" = ["REUSE.toml"]
+requires = ["setuptools>=43.0", "wheel>=0.33"]
+build-backend = "setuptools.build_meta"

--- a/setup.cfg	Tue Feb 17 17:16:27 2026 +0100
+++ b/setup.cfg	Tue Feb 17 17:18:10 2026 +0100
@@ -1,3 +1,5 @@
+# Build configuration for Python2.7 and older Python3 versions
+
 [egg_info]
 tag_build =
 tag_date = 0
@@ -6,6 +8,61 @@
 [bdist_wheel]
 universal = 1
 
+[sdist]
+formats = tar
+
+[metadata]
+name = py-cutils
+version = attr: cutils.__version__
+description = Pure Python implementation of some coreutils with some extensions
+author = Franz Glasner
+author_email = fzglas.hg@dom66.de
+license = BSD 3-Clause "New" or "Revised" License
+url = https://pypi.dom66.de/simple/py-cutils/
+download_url = https://pypi.dom66.de/simple/py-cutils/
+license_files =
+  LICENSES/BSD-3-Clause.txt
+  LICENSES/MIT.txt
+long_description = file: README.txt
+long_description_content_type = text/x-rst
+platforms = any
+classifiers =
+    Development Status :: 5 - Production/Stable
+    Environment :: Console
+    Intended Audience :: Developers
+    Intended Audience :: End Users/Desktop
+    Intended Audience :: System Administrators
+    License :: OSI Approved :: BSD License
+    License :: OSI Approved :: MIT License
+    Operating System :: OS Independent
+    Programming Language :: Python :: 2.7
+    Programming Language :: Python :: 3
+    Topic :: System
+    Topic :: Utilities
+
+[options]
+include_package_data = False
+zip_safe = True
+python_requires = >=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*
+packages =
+    cutils
+    cutils.util
+    cutils.crcmod
+    cutils.crcmod.python2
+    cutils.crcmod.python3
+
+[options.package_data]
+cutils.crcmod =
+    REUSE.toml
+
+[options.entry_points]
+console_scripts =
+    py-dos2unix = cutils.dos2unix:main
+    py-genpwd = cutils.genpwd:main
+    py-shasum = cutils.shasum:main
+    py-treesum = cutils.treesum:main
+
+
 [flake8]
 exclude =
     # Ignore the vendored crcmod2/crcmod sub-package