Share ccache between CI builds

.gitlab-ci.yml

@@ -5,18 +5,24 @@ before_script:
   - export LCG_hostos=x86_64-slc6
   - export PATH=/cvmfs/lhcb.cern.ch/lib/lhcb/LBSCRIPTS/dev/InstallArea/scripts:${PATH}
   - export CMAKE_PREFIX_PATH=/cvmfs/sft.cern.ch/lcg/releases:/cvmfs/projects.cern.ch/intelsw/psxe/linux/x86_64/2017/vtune_amplifier_xe
+  - export CCACHE_DIR=${PWD}/.ccache
 
 build:
   image: lhcbdev/slc6-build-cvmfs:latest
   stage: build
   script:
+    - curl -o artifacts.zip --location ${CI_PROJECT_URL}/builds/artifacts/master/download?job=build
+    - unzip -q artifacts.zip '.ccache/*' || true
+    - /cvmfs/sft.cern.ch/lcg/releases/ccache/3.3.4-e92e5/${BINARY_TAG}/bin/ccache -z
     - echo 'set(CMAKE_USE_CCACHE ON CACHE BOOL "")' >> cache_preload.cmake
     - make
+    - /cvmfs/sft.cern.ch/lcg/releases/ccache/3.3.4-e92e5/${BINARY_TAG}/bin/ccache -s
     - mv build.${BINARY_TAG} build
   artifacts:
     paths:
-      - build/
-    expire_in: 1 day
+      - build
+      - .ccache
+    expire_in: 1 week
 
 doxygen:
   image: lhcbdev/slc6-build-cvmfs:latest