Invalid (non-UTF8) characters found for option 'plugin_dir'

Steps:
1. Install an earlier version of the application (e.g. 10.7.1) in the non-ASCII parh (e.g. "C:\Program Files\Märiä")
2. Update to the 10.8 version (from preview-10.8-MDEV-26713-windows-i18-support branch)

Expected result
Update was successful, service is started.

Actual resul
Servic doesn't started:

Warning: C:\Program Files\Märiä\bin\mysql.exe: invalid (non-UTF8) characters found for option 'plugin_dir' in file 'C:\Program Files\Märiä\data\my.ini'

ERROR 2002 (HY000): Can't connect to server on 'localhost' (10061)