fix: replace a link at a standalone copy's name

A link already at the destination was skipped without a word and counted
as "dir not found" while the folder existed, so the emulator kept the file
the link pointed at. The link now gives way to the file, written beside it
and renamed over the name, and a name leading out of the folder is a named
failure.

tests/test_install.py

@@ -1608,6 +1608,9 @@ class TestStandaloneCopyTargetsAreUntrusted(unittest.TestCase):
         self.assertIsInstance(install._validate_manifest(manifest, "retroarch"), dict)
 
     def test_symlinked_destination_is_not_written_through(self):
+        """A link at the name was skipped in silence and counted as "dir
+        not found" while the folder existed: the emulator kept whatever the
+        link pointed at. The link now gives way to the file."""
         bios = Path(_tempdir(self))
         (bios / "boot.bin").write_text("rom")
         target = Path(_tempdir(self))
@@ -1615,12 +1618,17 @@ class TestStandaloneCopyTargetsAreUntrusted(unittest.TestCase):
         outside.write_text("untouched")
         (target / "boot.bin").symlink_to(outside)
 
-        copied, skipped, _ = install.do_standalone_copies(
-            self._manifest(str(target)), bios, "linux"
-        )
-        self.assertEqual(copied, 0)
-        self.assertEqual(skipped, 1)
+        out = io.StringIO()
+        with contextlib.redirect_stdout(out):
+            copied, skipped, failed = install.do_standalone_copies(
+                self._manifest(str(target)), bios, "linux"
+            )
+        self.assertEqual((copied, skipped, failed), (1, 0, 0))
         self.assertEqual(outside.read_text(), "untouched")
+        self.assertFalse((target / "boot.bin").is_symlink())
+        self.assertEqual((target / "boot.bin").read_text(), "rom")
+        self.assertIn("link replaced", out.getvalue())
+        self.assertEqual(sorted(p.name for p in target.iterdir()), ["boot.bin"])
 
 
 @unittest.skipUnless(shutil.which("pwsh"), "pwsh not available")