ggml-cpu.h is missing from public headers

[colintoal]

Trying to use llama.cpp as a dependency in my project, and ggml-cpu.h is not included in the public headers in ggml/CMakelists.txt. This may be intentional, but I am not at all sure why.

[slaren]

Should be fixed in the next sync after ggml-org/llama.cpp#10204 is merged.