fix: pass number of jobs to base image build

This argument was not moved over in the move to a linear image build, so build have been running at 1 core.

.gitlab-ci.yml

@@ -297,6 +297,7 @@ base:
                    --build-arg EICSPACK_VERSION=${EICSPACK_VERSION}
                    --build-arg S3_ACCESS_KEY=${S3_ACCESS_KEY}
                    --build-arg S3_SECRET_KEY=${S3_SECRET_KEY}
+                   --build-arg jobs=${JOBS}
                    --provenance false
                    containers/debian
                    2>&1 | tee build.log