[glibc] stdlib: Fix tst-stdbit-builtins.c build on clang-23

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=38abaa0b2127a8cd6a3aad29d2d5246f26cc9998

commit 38abaa0b2127a8cd6a3aad29d2d5246f26cc9998
Author: Adhemerval Zanella <[email protected]>
Date:   Mon Aug 24 16:49:30 2026 -0300

    stdlib: Fix tst-stdbit-builtins.c build on clang-23
    
    The 00e797cc20a703ae43f8df3ef557cf5ddd36d31b used a wrong ifdef
    for clang.

Diff:
---
 stdlib/tst-stdbit-builtins.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/stdlib/tst-stdbit-builtins.c b/stdlib/tst-stdbit-builtins.c
index 9236b8c111..ef7cd46d92 100644
--- a/stdlib/tst-stdbit-builtins.c
+++ b/stdlib/tst-stdbit-builtins.c
@@ -576,7 +576,7 @@ do_test (void)
   DIAG_POP_NEEDS_COMMENT_CLANG;
   /* clang-23 triggers an ICE with __builtin_stdc_bit_ceil with a non-constant
      unsigned _BitInt(1).  */
-#   ifdef __clang__
+#   ifndef __clang__
   unsigned _BitInt(1) c = 0;
   TEST_COMPARE (stdc_bit_floor (c++), 0);
   TEST_COMPARE (c, 1);