Fix cpp test report path issue.

Strangely the $(ls -d build_*) seems to fail sometimes as in https://gitlab.inria.fr/faustgrp/faust/-/jobs/3371149.

.gitlab-ci.yml

@@ -54,7 +54,7 @@ ctest:
         - linux
     artifacts:
         paths:
-            - $(ls -d build*  | tail -1)/cpp_test_report.html
+            - build_FaustLinux/cpp_test_report.html
             - ctest_coverage
         when:  always
         expire_in: '6 months'