Configure illink task to trim unreachable platform-specific code #31785
Description
IL linker is capable of constant propagation and dead code removal (see dotnet/linker#848).
We should configure linking for the runtime package to eliminate platform-specific unreachable code that is under conditions like:
- IntPtr.Size, sizeof(IntPtr)
- BitConverter.IsLittleEndian
- hardware intrinsics IsSupported methods
- System.Runtime.InteropService.OSPlatform