MDEV-32926 mysql_install_db_win fails on buildbot

- Do not suppress mysql_install_db.exe output in case of error
- Add --verbose-bootstrap to get errors coming from mysqld --boostrap

mysql-test/main/mysql_install_db_win.test

@@ -22,7 +22,9 @@ rmdir $ddir;
 # MDEV-23052
 # 1. mysql_install_db works on existing, empty directory
 mkdir $ddir;
-exec $MYSQL_INSTALL_DB_EXE --datadir=$ddir --password=foo -R > /dev/null;
+disable_result_log;
+exec $MYSQL_INSTALL_DB_EXE --datadir=$ddir --password=foo -R --verbose-bootstrap;
+enable_result_log;
 rmdir $ddir;
 
 # 2. mysql_install_db rejects existing, non-empty directory, and does not