gccrs: Add wrapper for make_unique

This is a wrapper for make_unique. We can likely get rid of this, as there
are other implementations available, or simply keep using the unique_ptr
constructor.

	gcc/rust/
	* util/rust-make-unique.h: New.

gcc/rust/util/rust-make-unique.h

@@ -0,0 +1,35 @@
+// Copyright (C) 2020-2022 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#ifndef RUST_MAKE_UNIQUE_H
+#define RUST_MAKE_UNIQUE_H
+
+#include "rust-system.h"
+
+namespace Rust {
+
+template <typename T, typename... Ts>
+std::unique_ptr<T>
+make_unique (Ts &&...params)
+{
+  return std::unique_ptr<T> (new T (std::forward<Ts> (params)...));
+}
+
+} // namespace Rust
+
+#endif // RUST_MAKE_UNIQUE_H