fix: EXT_SUFFIX wrong before 3.8.7

Signed-off-by: Henry Schreiner <[email protected]>

Author: henryiii

src/scikit_build_core/builder/builder.py

@@ -4,6 +4,7 @@
 import re
 import sys
 import sysconfig
+import typing
 from pathlib import Path
 from typing import Mapping
 
@@ -120,7 +121,15 @@ def configure(
             # Workaround for bug in PyPy and packaging that is not handled in CMake
             # According to PEP 3149, SOABI and EXT_SUFFIX are interchangeable (and
             # the latter is much more likely to be correct as it is used elsewhere)
-            ext_suffix = sysconfig.get_config_var("EXT_SUFFIX")
+            if sys.version_info < (3, 8, 7):
+                # See https://github.com/python/cpython/issues/84006
+                import distutils.sysconfig
+
+                ext_suffix = typing.cast(
+                    str, distutils.sysconfig.get_config_var("EXT_SUFFIX")
+                )
+            else:
+                ext_suffix = sysconfig.get_config_var("EXT_SUFFIX")
             assert ext_suffix
             cache_config["SKBUILD_SOABI"] = ext_suffix.rsplit(".", 1)[0].lstrip(".")