Whoever packaged the compiler.
If the packagers need support for their use case from the compiler, ex, they need to be able to tell the compiler “I’m going to put these files here” to make -print-file-name work, then it is on the packagers to communicate that the various compiler upstreams.
The compiler upstreams can decide on a case-by-case basis if they want to support the packagers conventions, or if it is on the packagers to align themselves with the compiler’s expectations.
CMake’s involvement begins and ends at -print-file-name. We 100% need better error messages if the path we get from -print-file-name is invalid, or the P3286 file contains bogus metadata, but we can’t “fix” that.