GitLab

Now that gitlab supports selecting which jobs to run
based on environment variables, it makes sense to build
those in the main branch

That version of gcc appears to be crashing when compiling
the latest version rocksdb, not sure why.. Maybe devtoolset-6
gcc can cope.

It appears that if rocksdb is compiled using tsan as well,
there are no more false positive data races - whooo. We
don't need the suppression file anymore. (which could potentially
mask real races)

https://bugzilla.redhat.com/show_bug.cgi?id=1481008