There are a ton of icalls that have no prototype on netcore and raise a warning as a result, at least when building for OSX, and any efforts to clean that up would be greatly appreciated.

For every warning you can #if netcore out the function, and what it uses, if there is no other use.

Or you can just squash the warning. Imho it isn't actually a useful warning.
The warning should only occur on the use, not the implementation, and if there is no use, as there isn't, then no warning.

And let the static linker do its job. It removes dead code well.
I don't see this actually making the runtime smaller, and it will mean that building for netcore gets less coverage of building for regular.
If regular is to be deleted in time then the #if helps that later effort.

Part of the point being, is that #if to remove code and other purposes is overused.
The code is often removed anyway by the static linker, and this means that building for configuration X fails to show errors from configuration Y.
It is better imho to if.
Many people agree, but not around here.
We should check if netcore is already smaller, i.e. due to icall-def-netcore.h.

Also, related: https://github.com/dotnet/coreclr/issues/25684 .