tidy: add unwinding as an allowed dependency

Add `unwinding` as a permitted dependency of rustc, as it is now used as
part of panic unwinding within platforms such as Xous.

Signed-off-by: Sean Cross <sean@xobs.io>

Author: xobs

src/tools/tidy/src/deps.rs

@@ -369,6 +369,7 @@ const PERMITTED_RUSTC_DEPENDENCIES: &[&str] = &[
     "unicode-security",
     "unicode-width",
     "unicode-xid",
+    "unwinding",
     "valuable",
     "version_check",
     "wasi",