Re: Meson 0.56.2 and Python39 --> dav1d failing

[Ken Cunningham]

dav1d is failing on 10.7 and 10.8 on the configure test for atomic.

it's building on 10.6 with clang 9.0, so probably needs to blacklist clangs 
older than 10.9's clang.

nothing to do with meson, looks to me...

K