[gcc r15-8414] gccrs: Add box definition to avoid error

[Arthur Cohen]

https://gcc.gnu.org/g:141b2f9c7bb9b4060d39a0ae404c50b0c71b5ba0

commit r15-8414-g141b2f9c7bb9b4060d39a0ae404c50b0c71b5ba0
Author: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>
Date:   Thu Sep 26 22:59:48 2024 +0200

    gccrs: Add box definition to avoid error
    
    Box definition is part of the standard library and cannot be found during
    name resolution. This simple definition prevent any error from being
    emitted.
    
    gcc/testsuite/ChangeLog:
    
            * rust/compile/box_syntax_feature_gate.rs: Add box land item
            definition.
    
    Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

Diff:
---
 gcc/testsuite/rust/compile/box_syntax_feature_gate.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/gcc/testsuite/rust/compile/box_syntax_feature_gate.rs b/gcc/testsuite/rust/compile/box_syntax_feature_gate.rs
index 8eb5503dde6c..5f62a59a04bf 100644
--- a/gcc/testsuite/rust/compile/box_syntax_feature_gate.rs
+++ b/gcc/testsuite/rust/compile/box_syntax_feature_gate.rs
@@ -1,4 +1,6 @@
 // { dg-options "-frust-compile-until=lowering" }
+#[lang = "owned_box"]
+pub struct Box<T>;
 
 fn main() {
     let x: Box<_> = box 1; //{ dg-error "box expression syntax is experimental." "" { target *-*-* }  }