(Re-)allow public_configs copying between toolchains.

tools/gn/target.cc

Index: tools/gn/target.cc
diff --git a/tools/gn/target.cc b/tools/gn/target.cc
index 759d7bff14493e59663830c67f2259562eb28f11..434cb86dd4fabfa0eb3ca785eacf4216a87a527a 100644
--- a/tools/gn/target.cc
+++ b/tools/gn/target.cc
@@ -352,10 +352,8 @@ bool Target::OnResolved(Err* err) {
   // private deps. This step re-exports them as public configs for targets that
   // depend on this one.
   for (const auto& dep : public_deps_) {
-    if (dep.ptr->toolchain() == toolchain()) {
-      public_configs_.Append(dep.ptr->public_configs().begin(),
-                             dep.ptr->public_configs().end());
-    }
+    public_configs_.Append(dep.ptr->public_configs().begin(),
+                           dep.ptr->public_configs().end());
   }
 
   // Copy our own libs and lib_dirs to the final set. This will be from our