Run apk upgrade in image used to build images

Axel von Bertoldirequested to merge
avonbertoldi/fix-curl-alpine-images into main

There's a problem with this image. Specifically with the curl installation. Without this step, attempting to run curl will yield

> curl
Error relocating /usr/bin/curl: curl_global_trace: symbol not found

e.g. https://gitlab.com/gitlab-org/gitlab-runner/-/jobs/5168919611

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