fix: use CXX=hipcc legacy mode for HIP CMake build

CMake 3.31 refuses CMAKE_HIP_COMPILER=hipcc with 'not supported'.
Using CXX=hipcc triggers the legacy HIP detection path which works.

ai/ollama/Dockerfile

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