Install gpg to verify build signatures if needed

docker/Dockerfile

@@ -10,7 +10,7 @@ RUN apk add --no-cache --update nginx git curl bash su-exec \
     php8-fpm php8-cli php8-phar php8-mysqli php8-session php8-mbstring \
     php8-iconv php8-xml php8-tokenizer php8-xmlwriter php8-simplexml \
     php8-dom php8-json php8-bz2 php8-curl php8-gd php8-zip php8-pecl-uploadprogress \
-    gettext yarn gpg-agent && \
+    gettext yarn gpg-agent gpg && \
     # https://gitlab.alpinelinux.org/alpine/aports/-/issues/12308
     ln -s /usr/bin/php8 /usr/bin/php && \
     mkdir -p /var/log/php8 && \