use macos-13 instead of macos-11

[mattip]

Change the gitub runner to macos-13 since macos-11 is deprecated.

[mattip]

The macos-x86_64 builds are failing with dyld[97241]: missing symbol called. I think this is when using one of the tools: gfortran, the linker, ... Anyone seen this when moving from macos-11 to macos-13?

[mattip]

Ahh, it seems /usr/local/lib is not added to the search path on x86_64, so the gfortran runtime shared objects are not found. I wonder if the x86_64 gfortran install should be soft-linking to a different path? @matthew-brett ideas? The apple documentation suggests /usr/local/lib should be in DYLD_FALLBACK_LIBRARY_PATH, but maybe it is not when using x86_64 on macos 13?

[mattip]

This was the best I found, apparently /usr/local/lib is no longer searched https://forums.developer.apple.com/forums/thread/737920