[gcc r14-8052] gccrs: Add new regression test

[Arthur Cohen]

https://gcc.gnu.org/g:46c84b78055325e2001ac6336f34e8ef5393db05

commit r14-8052-g46c84b78055325e2001ac6336f34e8ef5393db05
Author: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>
Date:   Tue Oct 10 16:03:45 2023 +0200

    gccrs: Add new regression test
    
    This new test highlight the fix for #2651.
    
    gcc/testsuite/ChangeLog:
    
            * rust/compile/macro_rules_macro_rules.rs: New test.
    
    Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

Diff:
---
 gcc/testsuite/rust/compile/macro_rules_macro_rules.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/gcc/testsuite/rust/compile/macro_rules_macro_rules.rs b/gcc/testsuite/rust/compile/macro_rules_macro_rules.rs
new file mode 100644
index 00000000000..ecd1712c94a
--- /dev/null
+++ b/gcc/testsuite/rust/compile/macro_rules_macro_rules.rs
@@ -0,0 +1,10 @@
+macro_rules! macro_rules {
+    () => {
+        struct S;
+    };
+}
+macro_rules! {} // calls the macro defined above
+
+fn main() {
+    let _s = S;
+}