Stable LbEnv, do not install graphviz, lhcb docker images

We need to use the LHCb docker image as opposed to the generic cc7
since it comes with the expected dependencies (HEP_OSlibs).

.gitlab-ci.yml

@@ -17,7 +17,8 @@ stages:
 variables:
   TARGET_BRANCH: master
   # Parameters for downloading nightlies and building Moore
-  CMTCONFIG: x86_64-centos7-gcc9-opt
+  BINARY_TAG: x86_64-centos7-gcc9-opt
+  NO_LBLOGIN: "1" # prevent lbdocker containers to start LbLogin/LbEnv
   LB_NIGHTLY_SLOT: lhcb-head
 
 check-copyright:
@@ -49,23 +50,24 @@ python-linting:
   tags:
     - cvmfs
   script:
-    - . /cvmfs/lhcb.cern.ch/lib/LbEnv-testing.sh
+    - . /cvmfs/lhcb.cern.ch/lib/LbEnv.sh
     # Only run the pyflakes linter
     - flake8 --select=F */python */options
 
 build:
   stage: build
+  image: gitlab-registry.cern.ch/lhcb-core/lbdocker/centos7-build:latest
   tags:
     - cvmfs
   script:
-    - . /cvmfs/lhcb.cern.ch/lib/LbEnv-testing.sh
+    - . /cvmfs/lhcb.cern.ch/lib/LbEnv.sh
     - . /cvmfs/lhcbdev.cern.ch/nightlies/${LB_NIGHTLY_SLOT}/latest/setupSearchPath.sh
     # Pick up the Phys and Allen builds from the nightly
     - sed -i 's/USE Phys v.*/USE Phys HEAD/' CMakeLists.txt
     - sed -i 's/Allen v.*/Allen HEAD/' CMakeLists.txt
     - lb-project-init
     - make CMAKEFLAGS=-DLOKI_BUILD_FUNCTOR_CACHE=OFF
-    - ln -s ./build.$CMTCONFIG/run run
+    - ln -s ./build.$BINARY_TAG/run run
   # Allow failure as the nightly slot we depend on may have itself failed
   allow_failure: true
   artifacts:
@@ -74,6 +76,7 @@ build:
 
 build-docs:
   stage: docs
+  image: gitlab-registry.cern.ch/lhcb-core/lbdocker/centos7-build:latest
   tags:
     - cvmfs
   # Change pip's cache directory so we can cache it
@@ -84,7 +87,6 @@ build-docs:
     # did not complete successfully (i.e. did not create the `run` symlink)
     - test -L run || exit 0
   script:
-    - yum install -y graphviz
     - ./run make -C doc linkcheck
     - ./run make -C doc html
   artifacts: