libfmt >=8.0.0 compatibility

src/modules/clock.cpp

@@ -196,6 +196,9 @@ template <>
 struct fmt::formatter<waybar_time> : fmt::formatter<std::tm> {
   template <typename FormatContext>
   auto format(const waybar_time& t, FormatContext& ctx) {
+#if FMT_VERSION >= 80000
+	auto& tm_format = specs;
+#endif
     return format_to(ctx.out(), "{}", date::format(t.locale, fmt::to_string(tm_format), t.ztime));
   }
 };