tui: flush -V3 ('verbose' >= 3) info ASAP

src/nvim/tui/tui.c

@@ -1073,9 +1073,12 @@ static void show_termcap_event(void **argv)
   if (!ut) {
     abort();
   }
+  verbose_enter();
   // XXX: (future) if unibi_term is modified (e.g. after a terminal
   // query-response) this is a race condition.
   terminfo_info_msg(ut);
+  verbose_leave();
+  verbose_stop();  // flush now
 }
 
 #ifdef UNIX

test/functional/terminal/tui_spec.lua

@@ -721,9 +721,6 @@ describe("tui", function()
       {3:-- TERMINAL --}                                    |
     ]])
 
-    -- Vim flushes the log file on exit.
-    feed_data('\33:q\n')
-
     retry(nil, 3000, function()  -- Wait for log file to be flushed.
       local log = read_file('Xtest_tui_verbose_log') or ''
       eq('--- Terminal info --- {{{\n', string.match(log, '--- Terminal.-\n'))