whitelist what we know works

If other people use other arch and want their builds to go faster we can
whitelist them too after they have confirmed it works.

core/base/Dockerfile

@@ -45,7 +45,7 @@ RUN set -euxo pipefail \
     { \
       machine="$(uname -m)" \
     ; deps="build-base gcc libffi-dev python3-dev" \
-    ; [[ "${machine}" == armv7 ]] && \
+    ; [[ "${machine}" != x86_64 ]] && \
         deps="${deps} cargo git libressl-dev mariadb-connector-c-dev postgresql-dev" \
     ; apk add --virtual .build-deps ${deps} \
     ; [[ "${machine}" == armv7 ]] && \