When using AppleClang the `clang` feature flag is not set, but the compiler supports `-flax-vector-conversions=integer`. This adds another `ADDITIONAL_COMPILE_FLAGS` for AppleClang to fix the CI.
When using AppleClang the `clang` feature flag is not set, but the compiler supports `-flax-vector-conversions=integer`. This adds another `ADDITIONAL_COMPILE_FLAGS` for AppleClang to fix the CI.