MDEV-20421: big_innodb_log reliably fails on buildbot Windows

The test fails because it reuses mysqltest perl code to copy directory
tree, and this code contains Windows-specific piece which outputs some
diagnostic information.

The patch introduces new parameter for that Windows-specific perl code to
have the ability to suppress diagnostic output on the corresponding
mysqltest perl module initialization.

mysql-test/lib/My/Handles.pm

@@ -24,8 +24,10 @@ use My::Platform;
 
 my $handle_exe;
 
-
-if (IS_WINDOWS){
+sub import {
+  my $self = shift;
+  my $params = shift;
+  return if (!IS_WINDOWS || $handle_exe);
   # Check if handle.exe is available
   # Pass switch to accept the EULA to avoid hanging
   # if the program hasn't been run before.
@@ -35,7 +37,7 @@ if (IS_WINDOWS){
     $handle_exe= "$2.$3"
       if ($line =~ /(Nth|H)andle v([0-9]*)\.([0-9]*)/);
   }
-  if ($handle_exe){
+  if ($handle_exe && (!$params || !$params->{suppress_init_messages})){
     print "Found handle.exe version $handle_exe\n";
   }
 }

mysql-test/suite/mariabackup/big_innodb_log.test

@@ -76,6 +76,7 @@ rmdir $targetdir;
 
 perl;
 use lib "lib";
+use My::Handles { suppress_init_messages => 1 };
 use My::File::Path;
 my $install_db_dir = ($ENV{MTR_PARALLEL} == 1) ?
   "$ENV{'MYSQLTEST_VARDIR'}/install.db" :