Vendor dependencies

Let's see how I like this workflow.

vendor/cxx/tools/buck/prelude/java/keystore.bzl

@@ -0,0 +1,18 @@
+# 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//java:java_providers.bzl", "KeystoreInfo")
+
+def keystore_impl(ctx: "context") -> ["provider"]:
+    sub_targets = {}
+    sub_targets["keystore"] = [DefaultInfo(default_outputs = [ctx.attrs.store])]
+    sub_targets["properties"] = [DefaultInfo(default_outputs = [ctx.attrs.properties])]
+
+    return [
+        KeystoreInfo(store = ctx.attrs.store, properties = ctx.attrs.properties),
+        DefaultInfo(default_outputs = [ctx.attrs.store, ctx.attrs.properties], sub_targets = sub_targets),
+    ]