Vendor dependencies

Let's see how I like this workflow.

vendor/cxx/tools/buck/prelude/python/compile.bzl

@@ -0,0 +1,35 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under both the MIT license found in the
+# LICENSE-MIT file in the root directory of this source tree and the Apache
+# License, Version 2.0 found in the LICENSE-APACHE file in the root directory
+# of this source tree.
+
+load(
+    ":manifest.bzl",
+    "ManifestInfo",  # @unused Used as a type
+)
+load(":toolchain.bzl", "PythonToolchainInfo")
+
+def compile_manifests(
+        ctx: "context",
+        manifests: [ManifestInfo.type],
+        ignore_errors: bool.type = False) -> "artifact":
+    output = ctx.actions.declare_output("bytecode")
+    cmd = cmd_args(ctx.attrs._python_toolchain[PythonToolchainInfo].host_interpreter)
+    cmd.add(ctx.attrs._python_toolchain[PythonToolchainInfo].compile)
+    cmd.add(cmd_args(output.as_output(), format = "--output={}"))
+    if ignore_errors:
+        cmd.add("--ignore-errors")
+    for manifest in manifests:
+        cmd.add(manifest.manifest)
+        cmd.hidden(manifest.artifacts)
+    ctx.actions.run(
+        cmd,
+        # On some platforms (e.g. linux), python hash code randomness can cause
+        # the bytecode to be non-deterministic, so pin via the `PYTHONHASHSEED`
+        # env var.
+        env = {"PYTHONHASHSEED": "7"},
+        category = "py_compile",
+    )
+    return output