[hb-view] Relax build requirements on cairo-ft

[behdad]

Currently we don't build hb-view if cairo-ft is not available. With hb-draw, that's not required anymore I believe. Can we test and relax that?

[behdad]

I do believe we still require freetype.

[khaledhosny]

I think I tried a while ago, it seems that freetype is still needed but probably can be worked out.

[behdad]

I'm trying to help @justvanrossum build hb-view on Mac, where he sees cairo as available but hb-view is not built. At least our messaging in meson configure is off as well. My guess is that his cairo lacks cairo-ft.