Updated comment

Author: UebelAndre

rust/private/rust.bzl

@@ -861,7 +861,11 @@ _rust_binary_attrs = {
         allow_single_file = True,
     ),
     "out_binary": attr.bool(
-        doc = "Force a target, regardless of it's `crate_type`, to always mark the file as executable.",
+        doc = (
+            "Force a target, regardless of it's `crate_type`, to always mark the " +
+            "file as executable. This attribute is only used to support wasm targets but is " +
+            "expected to be removed following a resolution to https://github.com/bazelbuild/rules_rust/issues/771."
+        ),
         default = False,
     ),
 }