[Bug libstdc++/110708] New: std::format("{:%EEC %OOd}", std::chrono::system_clock::now()) should be rejected

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110708

            Bug ID: 110708
           Summary: std::format("{:%EEC %OOd}",
                    std::chrono::system_clock::now()) should be rejected
           Product: gcc
           Version: 13.1.1
            Status: UNCONFIRMED
          Keywords: accepts-invalid
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

A chrono format string should only allow a single E or O modifier for each
flag.