Fixes https://github.com/harfbuzz/harfbuzz/issues/3017
Uses AdobeBlank2.ttf from:
https://github.com/adobe-fonts/adobe-blank-2
instead of a dummy empty font so that everything maps to GID 1 and
control code points are kept instead of being dropped because there is
not space glyph (otherwise we’d need to identify control code points
somehow when generating the expectations).
Khaled Hosny