[PATCH] rust: Fix rust modules test

[Daniel Xu]

I noticed that the modules test was failing. Some choice use of `nm`
revealed `TWENTY_THREE` was not in the final binary. Rather than trying
to trick the compiler/linker by using magic flags, simply `println!()`
the global.

gdb/testsuite/
        * gdb.rust/modules.rs: Prevent linker from discarding test
          symbol

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
---
 gdb/testsuite/gdb.rust/modules.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/gdb/testsuite/gdb.rust/modules.rs b/gdb/testsuite/gdb.rust/modules.rs
index 6db082817b..dc2a469b2f 100644
--- a/gdb/testsuite/gdb.rust/modules.rs
+++ b/gdb/testsuite/gdb.rust/modules.rs
@@ -93,4 +93,7 @@ pub mod mod1 {
 
 fn main () {
     mod1::inner::innest::f1();
+
+    // Prevent linker from discarding `TWENTY_THREE`
+    println!("{}", TWENTY_THREE);
 }
-- 
2.27.0