Failing Github actions workflow "Build/push Docker image (master/latest)"

[nodiscc]

Following #1867

https://github.com/shaarli/Shaarli/runs/7773366466?check_suite_focus=true

 > [stage-3 2/9] RUN apk --update --no-cache add         ca-certificates         nginx         php7         php7-ctype         php7-curl         php7-fpm         php7-gd         php7-iconv         php7-intl         php7-json         php7-mbstring         php7-openssl         php7-session         php7-xml         php7-simplexml         php7-zlib         s6:
#0 1.544   php7-openssl (no such package):
#0 1.544     required by: world[php7-openssl]
#0 1.544   php7-session (no such package):
#0 1.544     required by: world[php7-session]
#0 1.544   php7-simplexml (no such package):
#0 1.544     required by: world[php7-simplexml]
#0 1.544   php7-xml (no such package):
#0 1.544     required by: world[php7-xml]
#0 1.544   php7-zlib (no such package):
#0 1.544     required by: world[php7-zlib]

Error: buildx failed with: error: failed to solve: process "/bin/sh -c apk --update --no-cache add         ca-certificates         nginx         php7         php7-ctype         php7-curl         php7-fpm         php7-gd         php7-iconv         php7-intl         php7-json         php7-mbstring         php7-openssl         php7-session         php7-xml         php7-simplexml         php7-zlib         s6" did not complete successfully: exit code: 14

This workflow doesn't run on pull requests, hence this problem was not detected in the pull request, only after merging.

[nodiscc]

Proposed fix in #1869

This workflow doesn't run on pull requests, hence this problem was not detected in the pull request, only after merging.

-> #1800