Allow to decide whether to use distutils or sysconfig with sysconfig._PIP_USE_SYSCONFIG

Fixes pypa#10647

Author: hroncok

src/pip/_internal/locations/__init__.py

@@ -45,7 +45,11 @@
 
 _PLATLIBDIR: str = getattr(sys, "platlibdir", "lib")
 
-_USE_SYSCONFIG = sys.version_info >= (3, 10)
+# By default, we use sysconfig on Python 3.10+
+# But Python distributors can override this decision by setting:
+#     sysconfig._PIP_USE_SYSCONFIG = True / False
+# Rationale in https://github.com/pypa/pip/issues/10647
+_USE_SYSCONFIG = getattr(sysconfig, "_PIP_USE_SYSCONFIG", sys.version_info >= (3, 10))
 
 
 def _looks_like_bpo_44860() -> bool: