[gcc r17-3409] Add a pyproject.toml file

https://gcc.gnu.org/g:75754f5b1c3979125ea455e90a5ee20707ace549

commit r17-3409-g75754f5b1c3979125ea455e90a5ee20707ace549
Author: Claudio Bantaloukas <[email protected]>
Date:   Tue Aug 18 11:48:57 2026 +0000

    Add a pyproject.toml file
    
    The gcc repository has accrued a number of python
    scripts over time.
    They serve useful functions, but their dependencies
    are not extensively documented and this creates a
    needless barrier to their use. A pyproject.toml file,
    while not removing the ability of users to use their
    system's python interpreter and assorted
    distribution-provided python packages, makes it
    clear when some packages may have further
    requirements and allows use of the widely used
    pip and uv tools.
    
    The file is meant for gcc developers to use when
    hacking on gcc. As such, it will not install any
    script. Dependencies are expressed in as wide a
    range as possible with an upper limit on major
    versions of packages respecting semver rules.
    The exception is the black formatter, which is
    deliberately constrained to the 2026 edition in order
    to have a consistent and documented formatting target.
    
    Changelog:
            PR other/126226
            * .gitignore: Ignore python eggs.
            * pyproject.toml: New file.

Diff:
---
 .gitignore     |  1 +
 pyproject.toml | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 82 insertions(+)

diff --git a/.gitignore b/.gitignore
index f044fe16b5f6..ef1b4447f662 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,6 +15,7 @@
 *.lo
 *.o
 *.pyc
+*.egg-info
 *.tmp
 *.a
 
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 000000000000..32e3db611847
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,81 @@
+# Copyright (C) 2026 Free Software Foundation, Inc.
+#
+# This file is part of GCC.
+#
+# GCC is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+#
+# GCC is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GCC; see the file COPYING.  If not, write to
+# the Free Software Foundation, 51 Franklin Street, Fifth Floor,
+# Boston, MA 02110-1301, USA.
+
+# This pyproject.toml file is used to facilitate installation of all required
+# python dependencies.  It is not used to distribute gcc related packages.
+#
+# Users of uv can get all potentially needed with
+#   uv sync --all-groups
+# Whereas users of pip can use
+#   python -m pip install . --group all
+# Note that these include packages only used in a subset of projects.
+
+[build-system]
+requires = ["setuptools>=66.1"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "gcc"
+dynamic = ["version"]
+description = "Tools used when building and developing gcc"
+readme = "README"
+# As of August 2026, upstream python supports only versions from 3.10 and above.
+# Currently supported LTS distributions and unices all provide packages for
+# at least python 3.10.
+# pip added support for groups in 25.1 which requires python version 3.9
+# pytest-pyodide, used by libffi, requires python 3.10
+# black 26.0 requires python 3.10
+requires-python = ">=3.10"
+
+# Upper bounds below are conservative compatibility limits; not all projects
+# publish or strictly follow Semantic Versioning.
+dependencies = [
+	# we keep the black version pinned to an explicit calendar year
+	# in order to take advantage of black's stability policy.
+	"black ~= 26.0",
+	"GitPython<4",
+	"jsonschema<5",
+	"polib ~= 1.2.0",     # does not indicate use of semver
+	"pytest<10",
+	"python-dateutil<3",  # does not indicate use of semver
+	"PyYAML<7",           # does not indicate use of semver
+	"requests<3",
+	"semantic-version<3",
+	"Unidecode<2",        # does not indicate use of semver
+	"unidiff<2",          # does not indicate use of semver
+]
+
+[dependency-groups]
+ada = ["Pygments<3"]
+libffi = ["pytest-pyodide"]
+all = [
+	{ include-group = "ada" },
+	{ include-group = "libffi" },
+]
+
+[tool.setuptools]
+# Disable package discovery
+packages = []
+
+[tool.setuptools.dynamic]
+version = { file = ["gcc/BASE-VER"] }
+
+[tool.black]
+# target is same as requires-python
+target-version = ["py310"]