Add aarch64 prebuilts

[MarijnS95]

• ci: Add GCC multilib for missing headers
• build: Use neon ISA for arm/aarch64
• ci: Also generate aarch64 MacOS/iOS binaries
• ci: Build binaries for Linux and Android on aarch64

[MarijnS95]

https://github.com/Traverse-Research/ispc-downsampler/actions/runs/2590964100 Looks like everything built successfully, will upload these binaries if everyone is okay with the PR as a whole.