To help TSan.

A single find_package(harfbuzz) line in user code resulted in this loop
getting stuck when _harfbuzz_libdir_iter became "/".

See comment.

What were you thinking? ;)

To match FreeType units, such that FreeType gets correct size from us.
This matters more now that we allow setting --ft-load-flags.

Fixes https://github.com/harfbuzz/harfbuzz/pull/1179

Fixes https://github.com/harfbuzz/harfbuzz/issues/1175

Now I wonder if any bots will be unhappy we calling | in static const initializations...
Or would that cost runtime init?  Our tests don't detect any..

ubsan generates these.

Needed to make ubsan work.

Fixes https://github.com/harfbuzz/harfbuzz/issues/1174

Default exit value is 77, which causes autotools to "skip" test.