Gitlab CI integration: update submodules recursively

build.sh

 #!/bin/sh
 COVERAGE_DIR="coverage/$(basename "$PWD")/${CI_BUILD_REF_NAME}/${CI_BUILD_ID}"
-git submodule init 
-git submodule update
+source ./update.sh
 phpunit -c tests/phpunit.xml --coverage-text=coverage.txt --coverage-html="../${COVERAGE_DIR}"
 echo "</pre>"
 echo "<a href='/${COVERAGE_DIR}'>Code coverage</a>"