fix: pre-set CMAKE_HIP_COMPILER="" for CPU build to prevent HIP detection

ai/ollama/Dockerfile

@@ -42,12 +42,13 @@ ENV CMAKE_GENERATOR=Ninja
 ENV LDFLAGS=-s
 
 # Step 1: Build CPU backends with GCC (no ROCm preset)
-# Remove /opt/rocm from PATH to prevent check_language(HIP) from
-# finding a HIP compiler, which would trigger the HIP block that
-# requires find_package(hip) with proper CMAKE_PREFIX_PATH.
+# Pre-set CMAKE_HIP_COMPILER="" to prevent check_language(HIP) from
+# finding a HIP compiler (it searches /opt/rocm even without PATH).
+# Remove /opt/rocm from PATH to prevent find_program from finding hipcc.
 RUN mkdir -p build-cpu && cd build-cpu && \
     PATH=/usr/local/go/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin \
-    cmake .. -DCMAKE_BUILD_TYPE=Release && \
+    cmake .. -DCMAKE_BUILD_TYPE=Release \
+      -DCMAKE_HIP_COMPILER="" && \
     cmake --build . --target ggml-cpu -- -l $(nproc) && \
     cmake --install . --component CPU --strip --prefix /build/dist