Fix bootstrap install script on windows (astral-sh#1162)

Windows doesn't support symlinks, doesn't use a `bin` directory and all
pythons are called `python.exe`.

Note that this is still broken, `.\bin\python3.10.13` is missing its
.exe extension and renaming it to `.\bin\python3.10.13.exe` makes it
complain about not finding python310.dll.

scripts/bootstrap/install.py

@@ -1,4 +1,10 @@
 #!/usr/bin/env python3
+# /// script
+# requires-python = ">=3.11"
+# dependencies = [
+#   "zstandard==0.22.0",
+# ]
+# ///
 #
 # Download required Python versions and install to `bin`
 # Uses prebuilt Python distributions from indygreg/python-build-standalone
@@ -13,6 +19,10 @@
 #
 #   python scripts/bootstrap/install.py
 #
+# Or
+#
+#   pipx run scripts/bootstrap/install.py
+#
 # The Python versions are installed from `.python_versions`.
 # Python versions are linked in-order such that the _last_ defined version will be the default.
 #
@@ -96,8 +106,8 @@ def sha256_file(path: Path):
         print(f"No matching download for {key}")
         sys.exit(1)
 
+    filename = url.split("/")[-1]
     if not install_dir.exists():
-        filename = url.split("/")[-1]
         print(f"Downloading {urllib.parse.unquote(filename)}")
         download_path = THIS_DIR / filename
         with urllib.request.urlopen(url) as response:
@@ -129,28 +139,30 @@ def sha256_file(path: Path):
         already_exists = True
         print("Already available, skipping download")
 
-    # Use relative paths for links so if the bin is moved they don't break
-    executable = "." / install_dir.relative_to(BIN_DIR) / "install" / "bin" / "python3"
     if PLATFORM == "win32":
-        executable = executable.with_suffix(".exe")
+        executable = install_dir / "install" / "python.exe"
+    else:
+        # Use relative paths for links so if the bin is moved they don't break
+        executable = "." / install_dir.relative_to(BIN_DIR) / "install" / "bin" / "python3"
 
     major = versions_metadata[key]["major"]
     minor = versions_metadata[key]["minor"]
 
     # Link as all version tuples, later versions in the file will take precedence
     BIN_DIR.mkdir(parents=True, exist_ok=True)
-    targets = (
+
+    targets = [
         (BIN_DIR / f"python{version}"),
         (BIN_DIR / f"python{major}.{minor}"),
         (BIN_DIR / f"python{major}"),
         (BIN_DIR / "python"),
-    )
+    ]
     for target in targets:
-        if PLATFORM == "win32":
-            target = target.with_suffix(".exe")
-
         target.unlink(missing_ok=True)
-        target.symlink_to(executable)
+        if PLATFORM == "win32":
+            target.hardlink_to(executable)
+        else:
+            target.symlink_to(executable)
 
     if already_exists:
         print(f"Updated executables for python{version}")