[libclang/python] Enable packaging clang python bindings (#125806)

This adds a pyproject.toml file for packaging the clang Python bindings
as a sdist tarball and pure Python wheel packages for the clang python
bindings. It is required to move updates of the clang and libclang PyPI
packages to the LLVM monorepo. Versioning information is derived from
LLVM git tags (using hatch-vcs, which is based on setuptools_scm), so no
manual updates are needed to bump version numbers. The minimum python
version required is set to 3.10 due to cindex.py using PEP 604 union
type syntax (str | bytes | None).

The .git_archival.txt file is populated with version information needed
to get accurate version information if the bindings are installed from
an LLVM/clang source code archive. The .gitignore file is populated with
files that may get created as part of building/testing the sdist and
wheel that should not be committed to source control.

This is first step for addressing #125220, and moving publishing of the
clang and libclang PyPI packages into the LLVM monorepo.

Signed-off-by: Ryan Mast <mast.ryan@gmail.com>

.gitattributes

@@ -1,3 +1,5 @@
+clang/bindings/python/.git_archival.txt  export-subst
+
 libcxx/src/**/*.cpp     merge=libcxx-reformat
 libcxx/include/**/*.h   merge=libcxx-reformat
 

clang/bindings/python/.git_archival.txt

@@ -0,0 +1,3 @@
+node: $Format:%H$
+node-date: $Format:%cI$
+describe-name: $Format:%(describe:tags=true,match=llvmorg-*[0-9]*)$

clang/bindings/python/.gitignore

@@ -0,0 +1,21 @@
+# setuptools_scm auto-generated version file
+_version.py
+
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# Distribution / packaging
+build/
+dist/
+*.egg-info/
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/

clang/bindings/python/pyproject.toml

@@ -0,0 +1,43 @@
+[build-system]
+requires = ["hatchling>=1.27", "hatch-vcs>=0.4"]
+build-backend = "hatchling.build"
+
+[project]
+name = "clang"
+description = "clang python bindings"
+readme = {file = "README.txt", content-type = "text/plain"}
+
+license = "Apache-2.0 WITH LLVM-exception"
+authors = [
+    { name = "LLVM" }
+]
+keywords = ["llvm", "clang", "libclang"]
+classifiers = [
+    "Intended Audience :: Developers",
+    "Development Status :: 5 - Production/Stable",
+    "Topic :: Software Development :: Compilers",
+    "Operating System :: OS Independent",
+    "Programming Language :: Python :: 3",
+]
+requires-python = ">=3.8"
+dynamic = ["version"]
+
+[project.urls]
+Homepage = "https://clang.llvm.org/"
+Download = "https://llvm.org/releases/download.html"
+Discussions = "https://discourse.llvm.org/"
+"Issue Tracker" = "https://github.com/llvm/llvm-project/issues"
+"Source Code" = "https://github.com/llvm/llvm-project/tree/main/clang/bindings/python"
+
+[tool.hatch.version]
+source = "vcs"
+version-scheme = "no-guess-dev"
+# regex version capture group gets x.y.z with optional -rcN, -aN, -bN suffixes; -init is just consumed
+tag-pattern = "^llvmorg-(?P<version>\\d+(?:\\.\\d+)*(?:-rc\\d+)?)"
+
+[tool.hatch.build.hooks.vcs]
+version-file = "clang/_version.py"
+
+[tool.hatch.version.raw-options]
+search_parent_directories = true
+version_scheme = "no-guess-dev"