Make it possible to use CEF in universal macOS binaries

[vadz]

Right now this fails because building under x64 builds x64-only CEF wrapper (and downloads x64 version of CEF shared library), so linking doesn't find arm64 symbols.

I hope it is possible to use CEF in this case because Chrome itself does come up as a universal binary under Mac, but right now I don't really know how to do it: should we download both files and manually lipo all the shared libraries together?

And what about the support files, apparently at least the snapshot one is architecture-specific?

Any thoughts/hints would be welcome!

[vadz]

I don't see any other way than using lipo manually, CEF CMake makefiles explicitly override CMAKE_OSX_ARCHITECTURES and set it to CMAKE_HOST_SYSTEM_PROCESSOR, so we can't even build the wrapper library as a universal one.

I'll try to do this in my baby-cmake...

[vadz]

Without much surprise, my CMake-fu failed me, but I could at least create #24402 which solves this is another way.