Try to fix gitlab CI again

.gitlab-ci.yml

 image: debian:stretch
 
 before_script:
+  - dpkg --add-architecture i386
   - apt-get update
-  - apt-get install libx11-dev libc6-dev-i386 build-essential  -y
+  - apt-get install libx11-dev:i386 libc6-dev-i386 build-essential  -y
 
 smoke-test-by-make:
   stage: build