Vendor dependencies

Let's see how I like this workflow.

vendor/cxx/tools/buck/prelude/js/js.bzl

@@ -0,0 +1,74 @@
+# 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("@prelude//android:android.bzl", "android_toolchain")
+load("@prelude//js:js_bundle.bzl", "js_bundle_impl")
+load("@prelude//js:js_bundle_genrule.bzl", "js_bundle_genrule_impl")
+load("@prelude//js:js_library.bzl", "js_library_impl")
+load("@prelude//genrule.bzl", "genrule_attributes")
+
+def _select_platform():
+    # FIXME: prelude// should be standalone (not refer to ovr_config//)
+    return select({
+        "DEFAULT": "android",
+        "ovr_config//os/constraints:iphoneos": "ios",
+    })
+
+def _is_release():
+    # FIXME: prelude// should be standalone (not refer to ovr_config//)
+    return select({
+        "DEFAULT": False,
+        "ovr_config//build_mode/constraints:release": True,
+    })
+
+def _is_build_only_native_code():
+    return select(
+        {
+            "DEFAULT": False,
+            "fbsource//xplat/buck2/platform/android:build_only_native_code": True,
+        },
+    )
+
+implemented_rules = {
+    "js_bundle": js_bundle_impl,
+    "js_bundle_genrule": js_bundle_genrule_impl,
+    "js_library": js_library_impl,
+}
+
+extra_attributes = {
+    "js_bundle": {
+        "worker": attrs.exec_dep(),
+        "_android_toolchain": android_toolchain(),
+        "_is_release": attrs.bool(
+            default = _is_release(),
+        ),
+        "_platform": attrs.string(
+            default = _select_platform(),
+        ),
+    },
+    "js_bundle_genrule": genrule_attributes() | {
+        "type": attrs.string(
+            default = "js_bundle_genrule",
+        ),
+        "_is_release": attrs.bool(
+            default = _is_release(),
+        ),
+        "_platform": attrs.string(
+            default = _select_platform(),
+        ),
+    },
+    "js_library": {
+        "worker": attrs.exec_dep(),
+        "_build_only_native_code": attrs.bool(default = _is_build_only_native_code()),
+        "_is_release": attrs.bool(
+            default = _is_release(),
+        ),
+        "_platform": attrs.string(
+            default = _select_platform(),
+        ),
+    },
+}