Upgrade Mac OS libraries

All are updated except:

• WxWidgets (not sure about compatibility)
• libogg (doesn't compile)
• zlib/libsodimum which have no update.

This drops supports for 10.11 and earlier, meaning we can now assume SSE4.1 is present.
Updates the build system to account for this.

Closes #5777 (by virtue of upgrading to SDL 2.12)

Refs #4362

Differential Revision: https://code.wildfiregames.com/D3111