Build ports for ARM64 iOS simulator

[Stannieman]

Hi all!

We are at the point here where more and more iOS developers are having M1 machines and some of our CI build agents are ARM now as well. They would really like to use the ARM version of the iOS simulator and that means that the C++ libraries need to run on that too.
I am now trying to figure out how to make Vcpkg build dependencies for ARM64 simulator.

What would be required to do that?
I think ideally we should have a new arm64-iossimulator community triplet and then extend the scripts/toolchains/ios.cmake file to detect this. Is that right?
But how should this detection work? I feel we are missing something here. IMO TARGET_TRIPLET is not a good candidate because we are already using custom triplets to set our minimum iOS version, and we are probably not alone.

I also see:

If VCPKG_OSX_ARCHITECTURES or VCPKG_OSX_SYSROOT is set in the triplet, they will take priority,

does that mean that I can temporarily solve it by making a custom triplet and setting the VCPKG_OSX_SYSROOT in the triplet file?
Should we maybe set sysroot explicitly for all iOS triplets and get rid of this magic sysroot guessing altogether?