update: add blas installation for ARM CPUs

Author: inureyes

python/Dockerfile.3.9-ubuntu20.04

@@ -25,6 +25,11 @@ RUN apt-get update && \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/
 
+RUN apt-get update && \
+    apt-get install -y libopenblas-dev && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/
+
 ENV PYTHONUNBUFFERED=1 \
     PATH=/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin \
     LANG=C.UTF-8