PostLink: only stage icu 56 if it exists
PostLink: only stage icu 56 if it exists

otherwise use the installed version.
E.g. at the time of writing latest version 68 works great.

Hunter522/qgroundcontrol,Hunter522/qgroundcontrol,Hunter522/qgroundcontrol,Hunter522/qgroundcontrol,Hunter522/qgroundcontrol,Hunter522/qgroundcontrol