Feature/ci

Add different build targets Now there are

• clang8 coverage/release seq/mpi
• g++8 debug/release seq

.gitlab-ci/clang8-mpi-coverage.yml

+build:clang8-mpi-coverage:
+  image: localhost:5000/ubuntu_clang8_mpi
+  stage: build
+  script:
+    - mkdir -p build/clang8-cov-mpi
+    - cd build/clang8-cov-mpi
+    - CXX=clang++-8 CC=clang-8 cmake ../.. -DCMAKE_BUILD_TYPE=Coverage -DCLANG_FORMAT=/usr/bin/clang-format-8
+    - make pugs
+  cache:
+    key: "${CI_COMMIT_REF_SLUG}-clang8-cov-mpi"
+    paths:
+      - build/clang8-cov-mpi
+    untracked: true
+
+test:clang8-mpi-coverage:
+  image: localhost:5000/ubuntu_clang8_mpi
+  stage: test
+  dependencies:
+    - build:clang8-mpi-coverage
+  script:
+    - cd build/clang8-cov-mpi
+    - make coverage
+  cache:
+    key: "${CI_COMMIT_REF_SLUG}-clang8-cov-mpi"
+    paths:
+      - build/clang8-cov-mpi
+    untracked: true