Now we can build:
- arm64/x86_64 universal builds against 11.0
- x86_64 thin builds against 10.9
Which means no more support for 32-bit macOS (which I think excludes
macs made in 2011 or earlier) or for 10.8 (Mountain Lion) or earlier
(released in 2012 and possibly end-of-lifed in October 2015).