fix BUILDARCH ARG/ENV

Author: tschaume

mpcontribs-api/Dockerfile

@@ -25,7 +25,8 @@ RUN wget -q https://raw.githubusercontent.com/vishnubob/wait-for-it/master/wait-
   -O mpcontribs/api/contributions/formulae.json.gz
 
 FROM base
-ARG BUILDARCH=x86_64
+ARG BUILDARCH
+ENV BUILDARCH=x86_64
 COPY --from=builder /usr/local/lib/python3.11/site-packages /usr/local/lib/python3.11/site-packages
 COPY --from=builder /usr/local/bin /usr/local/bin
 COPY --from=builder /usr/lib/$BUILDARCH-linux-gnu/libsnappy* /usr/lib/$BUILDARCH-linux-gnu/