Add gitlab ci workflow

Mainly to check if the installation on ubuntu rolling works.

Change-Id: I19f7fd847fdeaf4c683a40b6f240cde211913779
diff --git a/.Rbuildignore b/.Rbuildignore
index 812333a..eb3f2c8 100644
--- a/.Rbuildignore
+++ b/.Rbuildignore
@@ -10,3 +10,5 @@
 ^CRAN-RELEASE$
 ^.*\.log$
 ^CRAN-SUBMISSION$
+^ci
+^.gitlab-ci