Fix access to _msvccompiler from newer distutils (pytorch#141363)

Newer versions of distutils no longer import `_msvccompiler` upon init(on Windows platform, that was not the case on other platforms even before 74), but it's still accessible if one chooses to import it directly.
Test plan:
```
% python -c 'from setuptools import distutils; print(distutils.__version__, hasattr(distutils, "_msvccompiler")); from distutils import _msvccompiler; import setuptools; print(setuptools.__version__, _msvccompiler.__file__)'
3.10.9 False
65.5.0 /usr/local/fbcode/platform010/Python3.10.framework/Versions/3.10/lib/python3.10/site-packages/setuptools/_distutils/_msvccompiler.py
```
and
```
% python -c 'from setuptools import distutils; print(distutils.__version__, hasattr(distutils, "_msvccompiler")); from distutils import _msvccompiler; import setuptools; print(setuptools.__version__, _msvccompiler.__file__)'
3.13.0 False
75.6.0 /Users/malfet/py312-venv/lib/python3.13/site-packages/setuptools/_distutils/_msvccompiler.py
```

Gave up trying to appease the linker, so rewrote it as following function:
```python
def _get_vc_env(vc_arch: str) -> dict[str, str]:
    try:
        from setuptools import distutils  # type: ignore[import]

        return distutils._msvccompiler._get_vc_env(vc_arch)  # type: ignore[no-any-return]
    except AttributeError:
        from setuptools._distutils import _msvccompiler  #type: ignore[import]

        return _msvccompiler._get_vc_env(vc_arch)  # type: ignore[no-any-return]
```

This PR also undoes setuptools version restriction introduced by  pytorch#136489 as premise for restriction is incorrect

Fixes pytorch#141319

Pull Request resolved: pytorch#141363
Approved by: https://github.com/huydhn, https://github.com/atalman

requirements.txt

@@ -6,10 +6,7 @@ numpy
 psutil
 pyyaml
 requests
-# Setuptools>=74.0.0 stopped support for directly using private funcs(_msvccompiler)
-# and consolidated all compiler logic in distutils used in Pytorch build, so older
-# is required until pytorch build not refactored to work for latest setuptools.
-setuptools<=72.1.0
+setuptools
 types-dataclasses
 typing-extensions>=4.10.0
 sympy==1.13.1 ; python_version >= "3.9"

tools/build_pytorch_libs.py

@@ -4,12 +4,21 @@
 import platform
 from glob import glob
 
-from setuptools import distutils  # type: ignore[import]
-
 from .setup_helpers.cmake import CMake, USE_NINJA
 from .setup_helpers.env import check_negative_env_flag, IS_64BIT, IS_WINDOWS
 
 
+def _get_vc_env(vc_arch: str) -> dict[str, str]:
+    try:
+        from setuptools import distutils  # type: ignore[import]
+
+        return distutils._msvccompiler._get_vc_env(vc_arch)  # type: ignore[no-any-return]
+    except AttributeError:
+        from setuptools._distutils import _msvccompiler  # type: ignore[import]
+
+        return _msvccompiler._get_vc_env(vc_arch)  # type: ignore[no-any-return]
+
+
 def _overlay_windows_vcvars(env: dict[str, str]) -> dict[str, str]:
     vc_arch = "x64" if IS_64BIT else "x86"
 
@@ -33,7 +42,7 @@ def _overlay_windows_vcvars(env: dict[str, str]) -> dict[str, str]:
                 "emulation is enabled!"
             )
 
-    vc_env: dict[str, str] = distutils._msvccompiler._get_vc_env(vc_arch)
+    vc_env = _get_vc_env(vc_arch)
     # Keys in `_get_vc_env` are always lowercase.
     # We turn them into uppercase before overlaying vcvars
     # because OS environ keys are always uppercase on Windows.

torch/utils/cpp_extension.py

@@ -2109,6 +2109,15 @@ def _get_num_workers(verbose: bool) -> Optional[int]:
     return None
 
 
+def _get_vc_env(vc_arch: str) -> dict[str, str]:
+    try:
+        from setuptools import distutils
+        return distutils._msvccompiler._get_vc_env(vc_arch)
+    except AttributeError:
+        from setuptools._distutils import _msvccompiler
+        return _msvccompiler._get_vc_env(vc_arch)
+
+
 def _run_ninja_build(build_directory: str, verbose: bool, error_prefix: str) -> None:
     command = ['ninja', '-v']
     num_workers = _get_num_workers(verbose)
@@ -2121,9 +2130,7 @@ def _run_ninja_build(build_directory: str, verbose: bool, error_prefix: str) ->
 
         plat_name = distutils.util.get_platform()
         plat_spec = PLAT_TO_VCVARS[plat_name]
-
-        vc_env = distutils._msvccompiler._get_vc_env(plat_spec)
-        vc_env = {k.upper(): v for k, v in vc_env.items()}
+        vc_env = {k.upper(): v for k, v in _get_vc_env(plat_spec).items()}
         for k, v in env.items():
             uk = k.upper()
             if uk not in vc_env: