moved composer hash to ARG

Dockerfile

@@ -1,5 +1,6 @@
 FROM php:7.2-rc-alpine
 
+ARG COMPOSER_HASH=544e09ee996cdf60ece3804abc52599c22b1f40f4323403c44d44fdfdd586475ca9813a858088ffbc1f233e9b180f061
 ARG DOCKER_COMPOSE_VERSION=1.15.0
 ARG RANCHER_COMPOSE_VERSION=0.12.5
 ARG RANCHERIZE_HOME=/home/rancherize
@@ -40,7 +41,7 @@ WORKDIR /opt/rancherize
 
 # install composer packages
 RUN php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');" \
-    && php -r "if (hash_file('SHA384', 'composer-setup.php') === '669656bab3166a7aff8a7506b8cb2d1c292f042046c5a994c43155c0be6190fa0355160742ab2e1c88d40d5be660b410') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;" \
+    && php -r "if (hash_file('SHA384', 'composer-setup.php') === '$COMPOSER_HASH') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;" \
     && php composer-setup.php \
     && php -r "unlink('composer-setup.php');" \
     && ./composer.phar install --no-dev && rm composer.phar