use load_symbols to override read_config and read_root_config into st…

…arlark defined one

Summary: We have starlark wrappers around read_config and read_root_config that basically add logging and easy to tweak.

Reviewed By: scottcao

Differential Revision: D67046846

fbshipit-source-id: 703cda6e6bd6eaacf0f35f9286d2f8036a19807c

prelude/prelude.bzl

@@ -6,6 +6,14 @@
 # of this source tree.
 
 load("@prelude//:native.bzl", _native = "native")
+load("@prelude//utils:buckconfig.bzl", _read_config = "read_config_with_logging", _read_root_config = "read_root_config_with_logging", log_buckconfigs = "LOG_BUCKCONFIGS")
+
+__overridden_builtins__ = {
+    "read_config": _read_config,
+    "read_root_config": _read_root_config,
+} if log_buckconfigs else {}
+
+load_symbols(__overridden_builtins__)
 
 # Public symbols in this file become globals everywhere except `bzl` files in prelude.
 # Additionally, members of `native` struct also become globals in `BUCK` files.