Add CUSTOM_CPU_FLAGS to Dockerfile. (#8284)

* Add CUSTOM_CPU_FLAGS.

* fix golangci-lint error.

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Co-authored-by: Richard Lyons <rick@frob.com.au>

Dockerfile

@@ -67,6 +67,7 @@ ARG OLLAMA_SKIP_CUDA_GENERATE
 ARG OLLAMA_SKIP_ROCM_GENERATE
 ARG OLLAMA_FAST_BUILD
 ARG VERSION
+ARG CUSTOM_CPU_FLAGS
 RUN --mount=type=cache,target=/root/.ccache \
     if grep "^flags" /proc/cpuinfo|grep avx>/dev/null; then \
         make -j $(nproc) dist ; \