Vendor dependencies

Let's see how I like this workflow.

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

@@ -0,0 +1,59 @@
+# 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//utils:utils.bzl", "expect", "value_or")
+
+def http_file_shared(
+        actions: "actions",
+        name: str.type,
+        url: str.type,
+        is_executable: bool.type,
+        is_exploded_zip: bool.type,
+        unzip_tool: [RunInfo.type, None],
+        sha1: [None, str.type],
+        sha256 = [None, str.type]) -> ["provider"]:
+    output = actions.declare_output(name)
+    downloaded_output = actions.declare_output("exploded_zip") if is_exploded_zip else output
+    actions.download_file(
+        downloaded_output,
+        url,
+        is_executable = is_executable,
+        sha1 = sha1,
+        sha256 = sha256,
+        is_deferrable = True,
+    )
+
+    if is_exploded_zip:
+        actions.run(
+            cmd_args([
+                unzip_tool,
+                "--src",
+                downloaded_output,
+                "--dst",
+                output.as_output(),
+            ]),
+            category = "exploded_zip_unzip",
+            local_only = sha1 == None,
+        )
+
+    providers = [DefaultInfo(default_outputs = [output])]
+    if is_executable:
+        providers.append(RunInfo(args = [output]))
+    return providers
+
+def http_file_impl(ctx: "context") -> ["provider"]:
+    expect(len(ctx.attrs.urls) == 1, "multiple `urls` not supported: {}", ctx.attrs.urls)
+    return http_file_shared(
+        ctx.actions,
+        name = value_or(ctx.attrs.out, ctx.label.name),
+        url = ctx.attrs.urls[0],
+        sha1 = ctx.attrs.sha1,
+        sha256 = ctx.attrs.sha256,
+        is_executable = ctx.attrs.executable or False,
+        is_exploded_zip = False,
+        unzip_tool = None,
+    )