Improve Docker build caching

First install the dependencies, then copy the files from the build context
into the image. This allows for more caching during rebuilds when files
change and rebuilds are much faster.

contrib/Dockerfile

@@ -35,10 +35,10 @@ RUN rm -f /app/import/* /app/config/config.php
 # Build the PHP container
 FROM php:7-fpm-alpine
 WORKDIR /var/www
-COPY --from=data /app/ /var/www
 RUN apk add --no-cache icu-dev gettext-dev && \
-    docker-php-ext-install intl gettext pdo_mysql && \
+    docker-php-ext-install intl gettext pdo_mysql
-    chown -R www-data:www-data /var/www/import/ /var/www/storage/ && \
+COPY --from=data /app/ /var/www
+RUN chown -R www-data:www-data /var/www/import/ /var/www/storage/ && \
     rm -r /var/www/html
 
 ENV TRUSTED_PROXIES 10.0.0.0/8,::ffff:10.0.0.0/8,\

contrib/nginx/Dockerfile

@@ -1,8 +1,8 @@
 FROM node:8-alpine as themes
 WORKDIR /app
+RUN apk add --no-cache yarn
 COPY resources/assets/ /app/resources/assets
 COPY .babelrc package.json webpack.config.js /app/
-RUN apk add --no-cache yarn
 RUN yarn install
 RUN yarn build