Try to make distutils not emit relative paths

src/pip/_internal/locations/__init__.py

@@ -90,15 +90,6 @@ def _fix_abiflags(parts: Tuple[str]) -> Iterator[str]:
         yield part
 
 
-def _default_base(*, user: bool) -> str:
-    if user:
-        base = sysconfig.get_config_var("userbase")
-    else:
-        base = sysconfig.get_config_var("base")
-    assert base is not None
-    return base
-
-
 @functools.lru_cache(maxsize=None)
 def _warn_mismatched(old: pathlib.Path, new: pathlib.Path, *, key: str) -> None:
     issue_url = "https://github.com/pypa/pip/issues/10151"
@@ -144,6 +135,13 @@ def get_scheme(
     isolated: bool = False,
     prefix: Optional[str] = None,
 ) -> Scheme:
+    if home is not None and not os.path.isabs(home):
+        home = os.path.join(os.getcwd(), home)
+    if root is not None and not os.path.isabs(root):
+        root = os.path.join(os.getcwd(), root)
+    if prefix is not None and not os.path.isabs(prefix):
+        prefix = os.path.join(os.getcwd(), prefix)
+
     old = _distutils.get_scheme(
         dist_name,
         user=user,
@@ -161,11 +159,9 @@ def get_scheme(
         prefix=prefix,
     )
 
-    base = prefix or home or _default_base(user=user)
     warning_contexts = []
     for k in SCHEME_KEYS:
-        # Extra join because distutils can return relative paths.
-        old_v = pathlib.Path(base, getattr(old, k))
+        old_v = pathlib.Path(getattr(old, k))
         new_v = pathlib.Path(getattr(new, k))
 
         if old_v == new_v: