Suppress "System is unknown to cmake" warning

Usage
1

I wrote a toolchain file for a proprietary platform covered by NDAs.
I was looking for a way to suppress the following warning that I can embed in the toolchain file itself.

This warning is for project developers.  Use -Wno-dev to suppress it.

System is unknown to cmake, create:
Platform/REDACTED to use this system, please post your config file on discourse.cmake.org so it can be added to cmake
2

I believe you’ll need to provide a suitable Platform/Foo.cmake module as well. You might be able to use the Generic platform as an alternative?

3

I cannot use Generic as there are many of these platforms.

Is there any documentation of what should go into the platform module besides the system name? Pointer sizes?