fix: use ROCm amdclang++ as HIP compiler, keep GCC for CPU code

Setting CXX=hipcc caused compilation failures on CPU backends (AVX
intrinsics). Now using GCC for CPU, ROCm's amdclang++ for HIP only.

ai/ollama/Dockerfile

@@ -42,13 +42,14 @@ ENV PATH=/opt/rocm/bin:/opt/rocm/hip/bin:/opt/rocm/hcc/bin:/usr/local/sbin:/usr/
 ENV CMAKE_GENERATOR=Ninja
 ENV LDFLAGS=-s
 
-# Build with ROCm 6 preset + gfx906 target (CXX=hipcc for legacy HIP mode)
+# Build with ROCm 6 preset + gfx906 target (ROCm clang for HIP, GCC for CPU)
 RUN mkdir -p build && cd build && \
-    CC=hipcc CXX=hipcc cmake .. \
+    cmake .. \
       --preset 'ROCm 6' \
       -DAMDGPU_TARGETS="gfx906:xnack-;gfx940;gfx1010;gfx1030;gfx1100;gfx1200" \
+      -DCMAKE_HIP_COMPILER=/opt/rocm/bin/amdclang++ \
       -DCMAKE_BUILD_TYPE=Release && \
-    CC=hipcc CXX=hipcc cmake --build . -- -l $(nproc) && \
+    cmake --build . -- -l $(nproc) && \
     cmake --install . --component HIP --strip --prefix /build/dist
 
 # Build the Go binary