Add the unreachable builtin function

gcc/elna-builtins.cc

@@ -73,6 +73,8 @@ namespace elna::gcc
         declare_builtin_type(symbol_table, "Float", elna_float_type_node);
         declare_builtin_type(symbol_table, "String", elna_string_type_node);
 
+        symbol_table->enter("unreachable", *elna_global_decls->get("__builtin_unreachable"));
+
         return symbol_table;
     }
 }