[GitLabCI] CI_DEBUG_TRACE=True.

.gitlab/ci/build.gitlab-ci.yml

@@ -29,6 +29,9 @@ build:ubuntu_cpp:
     paths:
       - build_cpp/
       - install_cpp/
+  variables:
+    CI_DEBUG_TRACE: "true"
+
 
 build:ubuntu_python:
   stage: build