gccrs: Define constructor for LoadedCrate struct

Aggregate initialization does not compile properly for LoadedCrate in C++20.

gcc/rust/ChangeLog:

	* rust-session-manager.h (Session::LoadedCrate): Add explicit constructor.

Signed-off-by: Yap Zhi Heng <yapzhhg@gmail.com>

Author: Polygonalr

gcc/rust/rust-session-manager.h

@@ -461,6 +461,11 @@ struct Session
 
   struct LoadedCrate
   {
+    LoadedCrate (std::string name, NodeId node_id,
+		 Resolver2_0::NameResolutionContext ctx)
+      : name (std::move (name)), node_id (node_id), ctx (std::move (ctx))
+    {}
+
     LoadedCrate (const LoadedCrate &) = delete;
     LoadedCrate &operator= (const LoadedCrate &) = delete;
     LoadedCrate (LoadedCrate &&other) = default;