MDEV-9409 workaround

mysql-test/r/mysqld--help.result

-Windows bug: happens when a new line is exactly at the right offset.
+Windows bug: new line disappears when it is exactly at the right offset.
 The following options may be given as the first argument:
 --print-defaults Print the program argument list and exit.
 --no-defaults Don't read default options from any option file.

mysql-test/t/mysqld--help.test

@@ -42,7 +42,7 @@ perl;
   $re2=join('|', @plugins);
   $skip=0;
   open(F, '<', "$ENV{MYSQL_TMP_DIR}/mysqld--help.txt") or die;
-  print "Windows bug: happens when a new line is exactly at the right offset.\n";
+  print "Windows bug: new line disappears when it is exactly at the right offset.\n";
   while (<F>) {
     next if 1../The following groups are read/;
     # formatting, skip line consisting entirely of dashes and blanks