setup-apkrepos - wget on https behind proxy
it seems there is a problem to get mirrors.txt (eg. MIRRORS_URL=https://mirrors.alpinelinux.org/mirrors.txt) behind a proxy.
this problem seems to come from wget (eg. busybox) that systematically fails with HTTP/1.1 400 Couldn't not parse URL.
the use of http:// in variable MIRRORS_URL would solve this inconvenience.