dpranke@ this has bit me a few times but I admit I wouldn't know
where to start looking for a solution, any pointers would be very
appreciated :-)

How would you determine the SDK version? Would you use something besides //chromeos/CHROMEOS_LKGM ?

If you wanted to enforce this at GN-time (like we do on Mac and Win), you can look at //build/config/win/visual_studio_version.gni or //build/config/mac/mac_sdk.gni. The basic idea is to launch a script to read something from somewhere to get the version, and then compare it to the minimum supported version in the gni file.

The SDK version would be explicitly determined by the owner of the Chromium CL that adds the dependency to a specific CrOS SDK version.

It can't be //chromeos/CHROMEOS_LKGM since that would force everyone to update their local SDK any time we have a new one, even if there is no new dependency.

A typical workflow is to pull down an sdk with 'cros chrome-sdk', then, at a later time, pull new code for Chromium, that might introduce a dependency to a new sdk.
Re-running 'cros chrome-sdk' won't download a new sdk unless --clear-sdk is specified.
So if a new dependency is introduced, you'll likely get a build error.

Enforcing it at GN-time would work.
When a new dependency is introduced, the author of the Chromium CL could bump up soomething like a min-version-required in a file in the Chromium tree. GN would then read that, and make clear a new chrome-sdk is needed if that's the case.

Archiving P3s older than 1 year with no owner or component.