This is just to make it harder to be extremely slow. There definitely
are ways still, just harder. Oh well... how do we tame this problem
without solving halting problem?!
Fixes https://github.com/behdad/harfbuzz/issues/174
To fully test what these are supposed to test, they should be run
against libharfbuzz-fuzzing.la instead of libharfbuzz.la, but for
now just record the files.
Also route fuzzing-related tests through hb-ot-font, to reduce dependency
on FreeType behavior for badly-broken fonts. Fixes failing test with
FreeType master.
Behdad Esfahbod