exit with non-zero status code when hash mismatch

[sudo-barun]

In case the hash does not match, exiting with non-zero value is useful during docker build.

For the following Dockerfile, the error during docker build occurs at the line RUN php composer-setup.php

# ...
RUN php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
RUN php -r "if (hash_file('sha384', 'composer-setup.php') === 'dac665fdc30fdd8ec78b38b9800061b4150413ff2e3b6f88543c636f7cd84f6db9189d43a81e5503cda447da73c7e5b6') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"
RUN php composer-setup.php
RUN php -r "unlink('composer-setup.php');"
# ...

After this update, docker build fails at the previous line: RUN php -r "if (hash_file('sha384', 'composer-setup.php') === 'dac665....