Allow files for `compat_label_flag()`'s label attributes `default_value`, `runtime` and `_native_target`, staying compatible with the prior `label_flag()` behaviour.

PiperOrigin-RevId: 971288432

bazel/private/compat_flag.bzl

diff --git a/bazel/private/compat_flag.bzl b/bazel/private/compat_flag.bzl
index acabfe3..8ffd0c9 100644
--- a/bazel/private/compat_flag.bzl
+++ b/bazel/private/compat_flag.bzl
@@ -222,8 +222,8 @@
 
 _COMMON_LABEL_FLAG_ATTRS = {
     "fragment_field": attr.string(),
-    "default_value": attr.label(),
-    "runtime": attr.label(),
+    "default_value": attr.label(allow_files = True),
+    "runtime": attr.label(allow_files = True),
     "scope": attr.string(),
 }
 
@@ -232,6 +232,7 @@
     if HAS_NATIVE_PROTO_FLAGS and fragment_name:
         attrs["_native_target"] = attr.label(
             default = configuration_field(fragment = "proto", name = fragment_name),
+            allow_files = True,
         )
     return rule(
         implementation = _compat_executable_label_rule_impl if executable else _compat_label_rule_impl,