[gcc r17-2463] libstdc++: Disable serialization test for piecewise_linear_distribution<double> on i686

https://gcc.gnu.org/g:d2a3bf4da621412d6fb574e117ff6046aaeaabb6

commit r17-2463-gd2a3bf4da621412d6fb574e117ff6046aaeaabb6
Author: Tomasz Kamiński <[email protected]>
Date:   Thu Jul 16 15:36:08 2026 +0200

    libstdc++: Disable serialization test for piecewise_linear_distribution<double> on i686
    
    The r17-2455-gf8c277ed801ba6 enabled test_custom unconditionally for both
    double and float, however all-combination test shows that double remains
    unstable.
    
    libstdc++-v3/ChangeLog:
    
            * testsuite/26_numerics/random/piecewise_linear_distribution/operators/serialize2.cc:
            Enable test_customd<double> for __x86_64__.

Diff:
---
 .../random/piecewise_linear_distribution/operators/serialize2.cc       | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/testsuite/26_numerics/random/piecewise_linear_distribution/operators/serialize2.cc b/libstdc++-v3/testsuite/26_numerics/random/piecewise_linear_distribution/operators/serialize2.cc
index 55f0d8c427d4..36157dea4e0f 100644
--- a/libstdc++-v3/testsuite/26_numerics/random/piecewise_linear_distribution/operators/serialize2.cc
+++ b/libstdc++-v3/testsuite/26_numerics/random/piecewise_linear_distribution/operators/serialize2.cc
@@ -104,8 +104,9 @@ int main()
   test_default<long double>();
 
   test_custom<float>();
+#ifdef __x86_64__
   test_custom<double>();
+#endif  
   test_custom<long double>();
-
   return 0;
 }