[Bug libstdc++/122698] New: syncbuf.cc is missing an include

[Stromeko at nexgo dot de via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122698

            Bug ID: 122698
           Summary: syncbuf.cc is missing an include
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: Stromeko at nexgo dot de
  Target Milestone: ---

Created attachment 62816
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=62816&action=edit
fix-syncbuf

On Cygwin a recent C++20 lib did not compile due to a missing #include <mutex>.