Add a --system flag for opt-in non-virtualenv installs (#2046)

## Summary

This is essentially a wrapper around something like `--python $(which
python3)`, but gives users a portable and streamlined way to solve the
common pain point of using `uv` in GitHub Actions or a Docker container.

See: https://github.com/astral-sh/uv/issues/1526.

scripts/check_system_python.py

@@ -0,0 +1,74 @@
+#!/usr/bin/env python3
+
+"""Install `pylint` into the system Python."""
+
+import argparse
+import logging
+import os
+import subprocess
+import sys
+import tempfile
+
+if __name__ == "__main__":
+    logging.basicConfig(level=logging.INFO, format="%(levelname)s: %(message)s")
+
+    print("sys.executable:: %s" % sys.executable)
+
+    parser = argparse.ArgumentParser(description="Check a Python interpreter.")
+    parser.add_argument("--uv", help="Path to a uv binary.")
+    args = parser.parse_args()
+
+    uv: str = os.path.abspath(args.uv) if args.uv else "uv"
+
+    # Create a temporary directory.
+    with tempfile.TemporaryDirectory() as temp_dir:
+        # Ensure that the package (`pylint`) isn't installed.
+        logging.info("Checking that `pylint` isn't installed.")
+        code = subprocess.run(
+            [sys.executable, "-m", "pip", "show", "pylint"],
+            cwd=temp_dir,
+        )
+        if code.returncode == 0:
+            raise Exception("The package `pylint` is installed.")
+
+        # Install the package (`pylint`).
+        logging.info("Installing the package `pylint`.")
+        subprocess.run(
+            [uv, "pip", "install", "pylint", "--system", "--verbose"],
+            cwd=temp_dir,
+            check=True,
+        )
+
+        # Ensure that the package (`pylint`) isn't installed.
+        logging.info("Checking that `pylint` is installed.")
+        code = subprocess.run(
+            [sys.executable, "-m", "pip", "show", "pylint"],
+            cwd=temp_dir,
+        )
+        if code.returncode != 0:
+            raise Exception("The package `pylint` isn't installed.")
+
+        # TODO(charlie): Windows is failing to find the `pylint` binary, despite
+        # confirmation that it's being written to the intended location.
+        if os.name != "nt":
+            logging.info("Checking that `pylint` is in the path.")
+            code = subprocess.run(["which", "pylint"], cwd=temp_dir)
+            if code.returncode != 0:
+                raise Exception("The package `pylint` isn't in the path.")
+
+        # Uninstall the package (`pylint`).
+        logging.info("Uninstalling the package `pylint`.")
+        subprocess.run(
+            [uv, "pip", "uninstall", "pylint", "--system", "--verbose"],
+            cwd=temp_dir,
+            check=True,
+        )
+
+        # Ensure that the package (`pylint`) isn't installed.
+        logging.info("Checking that `pylint` isn't installed.")
+        code = subprocess.run(
+            [sys.executable, "-m", "pip", "show", "pylint"],
+            cwd=temp_dir,
+        )
+        if code.returncode == 0:
+            raise Exception("The package `pylint` is installed.")