give laradock the ability to install custom composer version

workspace/Dockerfile

@@ -147,7 +147,12 @@ RUN echo "" >> ~/.bashrc && \
 # Update composer
 ARG COMPOSER_VERSION=2
 ENV COMPOSER_VERSION ${COMPOSER_VERSION}
-RUN composer self-update --${COMPOSER_VERSION}
+RUN set -eux; \
+      if [ "$COMPOSER_VERSION" = "1" ] || [ "$COMPOSER_VERSION" = "2" ]; then \
+          composer self-update --${COMPOSER_VERSION}; \
+      else \
+          composer self-update ${COMPOSER_VERSION}; \
+      fi
 
 USER laradock