phpoffice/phpspreadsheet 1.2.1 requires ext-gd * -> the requested PHP extension gd is missing from your system.

FROM php:7.2-alpine

RUN apk update
RUN apk add zlib-dev gd php7-gd
RUN docker-php-ext-install sockets pdo_mysql zip
RUN apk add --no-cache libpng libpng-dev && docker-php-ext-install gd

build:
    docker run --rm --tty --user $$(id -u):$$(id -g)
        --volume "$$(pwd)":/app
        --volume "$$(pwd)/ops/jenkins/github.token":/tmp/auth.json
        --volume "$$(pwd)/ops/jenkins/composer_trust_github.com":/root/.ssh/config
        composer install --no-dev
    rm -rf ops/docker/app.tar.gz
    tar -czvf ops/docker/app.tar.gz -X ops/jenkins/build_excludes .

docker run --rm --tty --user $(id -u):$(id -g)
    --volume "$(pwd)":/app
    --volume "$(pwd)/ops/jenkins/github.token":/tmp/auth.json
    --volume "$(pwd)/ops/jenkins/composer_trust_github.com":/root/.ssh/config
    --volume "$(pwd)/ops/jenkins/php/php.ini":/usr/local/etc/php/php.ini
    composer install --no-dev
[32mLoading composer repositories with package information[39m
[32mInstalling dependencies from lock file[39m
[37;41mYour requirements could not be resolved to an installable set of packages.[39;49m

  Problem 1
    - Installation request for phpoffice/phpspreadsheet 1.2.1 -> satisfiable by phpoffice/phpspreadsheet[1.2.1].
    - phpoffice/phpspreadsheet 1.2.1 requires ext-gd * -> the requested PHP extension gd is missing from your system.