python_binary: add a [debuginfo] subtarget

Summary:
This subtarget produces a json file with all debug information associated with the binary in the following format:

1. the file is a single list
2. each entry in the list is a pair of (location in buck-out, logical location), represented as a 2 element list
3. logical location refers to the place where the file would be in the par (next to the .so file), which (I think) is the same as the relative location in the `#debuginfo` folder

Reviewed By: itamaro

Differential Revision: D52905959

fbshipit-source-id: d0ee79d0a0d6b8ce7ccc2c6c9fea32aa33f99151

prelude/python/make_py_package.bzl

@@ -190,6 +190,8 @@ def make_py_package(
             allow_cache_upload = allow_cache_upload,
         )
         default.sub_targets[style] = make_py_package_providers(pex_providers)
+
+    default.sub_targets["debuginfo"] = _debuginfo_subtarget(ctx, debug_artifacts)
     return default
 
 def _make_py_package_impl(
@@ -325,6 +327,10 @@ def _make_py_package_impl(
         run_cmd = cmd_args(run_args).hidden([a for a, _ in runtime_files] + hidden_resources),
     )
 
+def _debuginfo_subtarget(ctx: AnalysisContext, debug_artifacts: list[(ArgLike, str)]) -> list[Provider]:
+    out = ctx.actions.write_json("debuginfo.manifest.json", debug_artifacts)
+    return [DefaultInfo(default_output = out, other_outputs = [a for a, _ in debug_artifacts])]
+
 def _preload_libraries_args(ctx: AnalysisContext, shared_libraries: dict[str, (LinkedObject, bool)]) -> cmd_args:
     preload_libraries_path = ctx.actions.write(
         "__preload_libraries.txt",