Build fail on self-built ROCm sdk

[daniandtheweb]

Building ggml with a self-built ROCm sdk results in the build failing, probably due to a different folder structure.
I've solved a similar issue on the Makefile of llama.cpp by allowing the compiler to look in another directory for the required files (ggerganov/llama.cpp@30e238b), but the CMakeFile seems to work differently and I'm unable to find a way to fix it.

[daniandtheweb]

I've opened a pr to fix the issue: #847.