dwarf: flush wip_nav after emitting anyerror type info

This caused a missing reference for u16 to not be emitted. Triggered
after removing something from start.zig which transitively added u16
to the module.

src/link/Dwarf.zig

@@ -3845,6 +3845,7 @@ pub fn flushModule(dwarf: *Dwarf, pt: Zcu.PerThread) FlushError!void {
         }
         if (global_error_set_names.len > 0) try uleb128(diw, @intFromEnum(AbbrevCode.null));
         try dwarf.debug_info.section.replaceEntry(wip_nav.unit, wip_nav.entry, dwarf, wip_nav.debug_info.items);
+        try wip_nav.flush(.unneeded);
     }
 
     {