GH-45867: [Python] Fix SetuptoolsDeprecationWarning (#47141)

### Rationale for this change
When building locally, I get many errors along the lines of

```
Please ensure the files specified are contained by the root
of the Python package (normally marked by `pyproject.toml`).

By 2026-Mar-20, you need to update your project and remove deprecated calls
or your builds will no longer be supported.

See https://packaging.python.org/en/latest/specifications/glob-patterns/ for details.
```

<img width="958" height="755" alt="terminal demo" src="https://github.com/user-attachments/assets/67f0e261-c4d2-403c-b004-688dfaaccda6" />

### What changes are included in this PR?
- Make the licence [SPDX compliant](https://spdx.org/licenses)
- Remove the licence classifier
- Move the licence files from `setup.cfg` to `pyproject.toml`
- Fix the [disallowed glob patterns](https://packaging.python.org/en/latest/specifications/glob-patterns) via symlinks
- Bumped the minimum version of `setuptools` due to macOS CI failures (don't know why this happened, caching maybe?)

I appreciate the symlink change might prove controversial. See discussions in #45867, fixes #45867.

### Are these changes tested?
When I rebuild locally, I get no errors any more.

### Are there any user-facing changes?
Yes. The minimum required version of `setuptools` is now `77`. However, this is available on `>=3.9` so won't affect anyone really.

* GitHub Issue: #45867

Authored-by: Patrick J. Roddy <[email protected]>
Signed-off-by: Antoine Pitrou <[email protected]>

Author: paddyroddy

ci/conda_env_python.txt

@@ -28,5 +28,5 @@ numpy>=1.16.6
 pytest
 pytest-faulthandler
 s3fs>=2023.10.0
-setuptools>=64
+setuptools>=77
 setuptools_scm>=8

python/.gitignore

@@ -45,3 +45,8 @@ pyarrow/_table_api.h
 manylinux1/arrow
 nm_arrow.log
 visible_symbols.log
+
+# the purpose of the custom SDist class in setup.py is to include these files
+# in the sdist tarball, but we don't want to track duplicates
+LICENSE.txt
+NOTICE.txt

python/pyproject.toml

@@ -22,7 +22,7 @@ requires = [
     # configuring setuptools_scm in pyproject.toml requires
     # versions released after 2022
     "setuptools_scm[toml]>=8",
-    "setuptools>=64",
+    "setuptools>=77",
 ]
 build-backend = "setuptools.build_meta"
 
@@ -32,9 +32,12 @@ dynamic = ["version"]
 requires-python = ">=3.10"
 description = "Python library for Apache Arrow"
 readme = {file = "README.md", content-type = "text/markdown"}
-license = {text = "Apache Software License"}
+license = "Apache-2.0"
+license-files = [
+    "LICENSE.txt",
+    "NOTICE.txt",
+]
 classifiers  = [
-    'License :: OSI Approved :: Apache Software License',
     'Programming Language :: Python :: 3.10',
     'Programming Language :: Python :: 3.11',
     'Programming Language :: Python :: 3.12',

python/requirements-build.txt

@@ -1,4 +1,4 @@
 cython>=3.1
 numpy>=1.25
 setuptools_scm>=8
-setuptools>=64
+setuptools>=77

python/setup.cfg

@@ -15,11 +15,6 @@
 # specific language governing permissions and limitations
 # under the License.
 
-[metadata]
-license_files =
-  ../LICENSE.txt
-  ../NOTICE.txt
-
 [build_sphinx]
 source-dir = doc/
 build-dir  = doc/_build

python/setup.py

@@ -23,6 +23,7 @@
 from os.path import join as pjoin
 import re
 import shlex
+import shutil
 import sys
 import warnings
 
@@ -33,6 +34,7 @@
     from distutils import sysconfig
 
 from setuptools import setup, Extension, Distribution
+from setuptools.command.sdist import sdist
 
 from Cython.Distutils import build_ext as _build_ext
 import Cython
@@ -395,11 +397,41 @@ def has_ext_modules(foo):
         return True
 
 
+class CopyLicenseSdist(sdist):
+    """Custom sdist command that copies license files from parent directory."""
+
+    def make_release_tree(self, base_dir, files):
+        # Call parent to do the normal work
+        super().make_release_tree(base_dir, files)
+
+        # Define source (parent dir) and destination (sdist root) for license files
+        license_files = [
+            ("LICENSE.txt", "../LICENSE.txt"),
+            ("NOTICE.txt", "../NOTICE.txt"),
+        ]
+
+        for dest_name, src_path in license_files:
+            src_full = os.path.join(os.path.dirname(__file__), src_path)
+            dest_full = os.path.join(base_dir, dest_name)
+
+            # Remove any existing file/symlink at destination
+            if os.path.exists(dest_full) or os.path.islink(dest_full):
+                os.unlink(dest_full)
+
+            if not os.path.exists(src_full):
+                msg = f"Required license file not found: {src_full}"
+                raise FileNotFoundError(msg)
+
+            shutil.copy2(src_full, dest_full)
+            print(f"Copied {src_path} to {dest_name} in sdist")
+
+
 setup(
     distclass=BinaryDistribution,
     # Dummy extension to trigger build_ext
     ext_modules=[Extension('__dummy__', sources=[])],
     cmdclass={
-        'build_ext': build_ext
+        'build_ext': build_ext,
+        'sdist': CopyLicenseSdist,
     },
 )