gitlab-ci: reduce the number of scons build

It seems overkill to me to build scons 7x for every pipeline.
Scons is now build with the oldest llvm version in scons-old-llvm
and with the newest llvm version in scons.

Signed-off-by: Samuel Pitoiset <>
Reviewed-by: Michel Dänzer <>
Reviewed-by: Eric Anholt <>
39 jobs for !2830 with ci-scons-opt in 52 minutes and 56 seconds (queued for 15 seconds)
merge request