add security:checker to composer build

.run_composer_audit: &run_composer_audit |

  if [ -e $COMPOSER_INSTALL_DIR/composer.lock ];

  then

    php security-checker security:check $COMPOSER_INSTALL_DIR/composer.lock

  fi

.run_composer_install: &run_composer_install |

  if [ -e $COMPOSER_INSTALL_DIR/composer.json ];

  then

.build_composer:

  stage: build

  image: registry.cetera.su/adm/adm/php_composer:stretch_5

  image: registry.cetera.su/adm/adm/php_composer:stretch_6

  variables:

    COMPOSER_INSTALL_DIR: ${CI_PROJECT_DIR}

  script:

    - *run_composer_audit

    - *run_composer_install

  only:

    refs: