[CI] add simple CI

.gitlab-ci.yml

+image: "flowdalic/debian-testing-dev:1.14"
+
+before_script:
+  - |
+    readarray TOOLS <<EOF
+    cc
+    gcc
+    EOF
+    for tool in ${TOOLS[@]}; do
+      echo -n "$tool version: "
+      $tool --version
+    done
+
+test-eval:
+  script:
+    - make