newer alpine (for newer PHP) and apk upgrade #1655

Dockerfile

@@ -26,7 +26,7 @@ RUN cd shaarli \
 
 # Stage 4:
 # - Shaarli image
-FROM alpine:3.8
+FROM alpine:3.12
 LABEL maintainer="Shaarli Community"
 
 RUN apk --update --no-cache add \
@@ -46,7 +46,8 @@ RUN apk --update --no-cache add \
         php7-xml \
         php7-simplexml \
         php7-zlib \
-        s6
+        s6 \
+	&& apk -U upgrade
 
 COPY .docker/nginx.conf /etc/nginx/nginx.conf
 COPY .docker/php-fpm.conf /etc/php7/php-fpm.conf