Building HIP on Ubuntu with RX 7800XT

[bartekrey]

Hi, I'm so sorry to take your time, but I would really like to make this work.
I'm on Ubuntu with AMD RX 7800XT. It's not officially supported by ROCm, and I previously struggled to install ROCm, however I installed Ollama with ease and I noticed it installed ROCm as well and it seems to work, however I would like to move to llama.cpp as it seems to be more efficient.
rocminfo | grep gfx | head -1 | awk '{print $2}' returns gfx1101, so it feels like it should work.

I can also build llama.cpp for CPU without any problems.

However, when I attempt to build with HIP:
HIPCXX="$(hipconfig -l)/clang" HIP_PATH="$(hipconfig -R)" \ cmake -S . -B build -DGGML_HIP=ON -DAMDGPU_TARGETS=gfx1100 -DCMAKE_BUILD_TYPE=Release \ && cmake --build build --config Release -- -j 16

I get:
CMake Error at /usr/share/cmake-3.30/Modules/CMakeDetermineHIPCompiler.cmake:49 (message): Could not find compiler set in environment variable HIPCXX: /usr/bin/clang. Call Stack (most recent call first): ggml/src/ggml-hip/CMakeLists.txt:36 (enable_language)

And indeed /usr/bin/clang does not exist, I have a shit tone of other files starting with clang there. My first intuition would be to do sudo apt install clang but I already read somewhere that it's not recommendable, as the build might require a specific version.

Additionally, I might immediately ask about something I will need if this is successful - the build documentation says:

The environment variable [HIP_VISIBLE_DEVICES] can be used to specify which GPU(s) will be used. If your GPU is not officially supported you can use the environment variable [HSA_OVERRIDE_GFX_VERSION] set to a similar GPU, for example 10.3.0 on RDNA2 (e.g. gfx1030, gfx1031, or gfx1035) or 11.0.0 on RDNA3.

This tells me I should in the future set [HSA_OVERRIDE_GFX_VERSION]=11.0.0 however I'm not sure where this environmental variable is going to be located, I'm only familiar with environmental variables stored in an .env file...

I would love to get some help with this, but I'm afraid the answer is either super simple or that it's impossible without ROCm support.