Upgrade CI scripts and Ctests to prepare the MPI version

.gitlab/build.yml

+---
+.build_script_template: &build_script
+  stage: build
+  tags: ["large"]
+  artifacts:
+    name: spm_build_${VERSION}
+    expire_in: 180 minutes
+    untracked: true
+    paths:
+      - install-${VERSION}
+      - build
+      - spm-build-${VERSION}.log
+  script:
+    - cd build
+    - cmake -DSPM_CI_VERSION=${VERSION}
+            -C ../.gitlab/ci-test-initial-cache.cmake  ..
+    - make -j 4 | tee ../spm-build-${VERSION}.log
+    - make install | tee -a ../spm-build-${VERSION}.log
+  only:
+    - branches
+    - master@solverstack/spm
+
+.build_script_template_seq: &build_script_seq
+  extends:
+    - .build_script_template
+    - .only-branches-seq
+
+.build_script_template_mpi: &build_script_mpi
+  extends:
+    - .build_script_template
+    - .only-branches-mpi
+
+build_spm_seq:
+  <<: *build_script_seq
+  variables:
+    VERSION: seq
+
+build_spm_mpi:
+  <<: *build_script_mpi
+  variables:
+    VERSION: mpi