[gcc r14-7650] gccrs: attributes: Add allow_internal_unstable attribute

[Arthur Cohen]

https://gcc.gnu.org/g:432120dc19ac0fe7323bdd4678ae26b45e34844e

commit r14-7650-g432120dc19ac0fe7323bdd4678ae26b45e34844e
Author: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>
Date:   Tue Jun 6 18:45:36 2023 +0200

    gccrs: attributes: Add allow_internal_unstable attribute
    
    Add allow_internal_unstable to the attribute table in order for it to be
    flagged as builtin.
    
    gcc/rust/ChangeLog:
    
            * util/rust-attributes.cc: Add attribute to the table.

Diff:
---
 gcc/rust/util/rust-attributes.cc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/gcc/rust/util/rust-attributes.cc b/gcc/rust/util/rust-attributes.cc
index 63bb57f3cd4..3a33d0629f2 100644
--- a/gcc/rust/util/rust-attributes.cc
+++ b/gcc/rust/util/rust-attributes.cc
@@ -33,6 +33,7 @@ static const BuiltinAttrDefinition __definitions[]
      {"cfg_attr", EXPANSION},
      {"deprecated", STATIC_ANALYSIS},
      {"allow", STATIC_ANALYSIS},
+     {"allow_internal_unstable", STATIC_ANALYSIS},
      {"doc", HIR_LOWERING},
      {"must_use", STATIC_ANALYSIS},
      {"lang", HIR_LOWERING},