build llama-cpp on CI, windows + arm64

[jcar87]

• build llama-cpp for Windows+arm64, both natively on Windows-11-arm and crossbuilt from Windows-11-arm
• Update tutorial for this. Note that llama-cpp requires clang to be built for arm64 Windows
• Disable OpenMP by default as clang-cl is required which links it to a different runtime
• The conan profile in the folder tries to automate the detection of the clang version and the matching msvc toolset - works as long as clang is installed with the Visual Studio Installer