[gcc r16-3671] libstdc++: fix makefile.in for syncbuf.lo

[Nathan Myers]

https://gcc.gnu.org/g:de35b739a849d6bc6d1b0978dbcdc737dd709c89

commit r16-3671-gde35b739a849d6bc6d1b0978dbcdc737dd709c89
Author: Nathan Myers <ncm@cantrip.org>
Date:   Mon Sep 8 15:33:23 2025 -0400

    libstdc++: fix makefile.in for syncbuf.lo
    
    This patch fixes Makefile.in to include mention of new syncbuf.lo.
    
    libstdc++-v3/Changelog:
            * src/c++20/Makefile.in: Mention syncbuf.lo.

Diff:
---
 libstdc++-v3/src/c++20/Makefile.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libstdc++-v3/src/c++20/Makefile.in b/libstdc++-v3/src/c++20/Makefile.in
index 1e005ae3c14e..104ee597b5ec 100644
--- a/libstdc++-v3/src/c++20/Makefile.in
+++ b/libstdc++-v3/src/c++20/Makefile.in
@@ -121,7 +121,7 @@ CONFIG_CLEAN_FILES =
 CONFIG_CLEAN_VPATH_FILES =
 LTLIBRARIES = $(noinst_LTLIBRARIES)
 libc__20convenience_la_LIBADD =
-am__objects_1 = tzdb.lo format.lo atomic.lo clock.lo
+am__objects_1 = tzdb.lo format.lo atomic.lo clock.lo syncbuf.lo
 @ENABLE_EXTERN_TEMPLATE_TRUE@am__objects_2 = sstream-inst.lo
 @GLIBCXX_HOSTED_TRUE@am_libc__20convenience_la_OBJECTS =  \
 @GLIBCXX_HOSTED_TRUE@	$(am__objects_1) $(am__objects_2)