Try ccache on gitlab

ci/gitlab/.gitlab-ci.yml

@@ -16,6 +16,8 @@ variables:
   UBUNTU_BIONIC_PR_INSTALLIMAGE: ${CI_REGISTRY_IMAGE}:ci-install-${CI_COMMIT_REF_SLUG}-UBUNTU_BIONIC
   UBUNTU_XENIAL_PR_INSTALLIMAGE: ${CI_REGISTRY_IMAGE}:ci-install-${CI_COMMIT_REF_SLUG}-UBUNTU_XENIAL
 
+  CCACHE_DIR: $CI_PROJECT_DIR/ccache
+
   GIT_SUBMODULE_STRATEGY: recursive
 
 Docker Setup:
@@ -58,6 +60,10 @@ coverage:
     TEST_SOTA_PACKED_CREDENTIALS: "$CI_PROJECT_DIR/credentials.zip"
   image: "$UBUNTU_BIONIC_PR_IMAGE"
   stage: test
+  cache:
+    key: "$CI_JOB_NAME"
+    paths:
+      - ccache/
   artifacts:
     paths:
       - build-coverage/coverage/
@@ -72,6 +78,10 @@ nop11:
     TEST_WITH_TESTSUITE: '0'
   image: "$UBUNTU_BIONIC_PR_IMAGE"
   stage: test
+  cache:
+    key: "$CI_JOB_NAME"
+    paths:
+      - ccache/
   script:
     - ./scripts/test.sh
 
@@ -88,6 +98,10 @@ debian-build+static:
     TEST_WITH_DOCS: '1'
   image: "$DEBIAN_TESTING_PR_IMAGE"
   stage: test
+  cache:
+    key: "$CI_JOB_NAME"
+    paths:
+      - ccache/
   script:
     - ./scripts/test.sh
 
@@ -99,6 +113,10 @@ bionic-pkg:
 
   image: "$UBUNTU_BIONIC_PR_IMAGE"
   stage: test
+  cache:
+    key: "$CI_JOB_NAME"
+    paths:
+      - ccache/
   artifacts:
     paths:
       - build-bionic/pkg
@@ -114,6 +132,10 @@ xenial-pkg:
 
   image: "$UBUNTU_XENIAL_PR_IMAGE"
   stage: test
+  cache:
+    key: "$CI_JOB_NAME"
+    paths:
+      - ccache/
   artifacts:
     paths:
       - build-xenial/pkg

docker/Dockerfile.debian.testing

@@ -11,6 +11,7 @@ RUN apt-get update && apt-get -y install \
   autoconf \
   automake \
   bison \
+  ccache \
   clang-6.0 \
   clang-tidy-6.0 \
   clang-tools-6.0 \

docker/Dockerfile.ubuntu.bionic

@@ -11,6 +11,7 @@ RUN apt-get update && apt-get -y install \
   asn1c \
   automake \
   bison \
+  ccache \
   clang-format-6.0 \
   cmake \
   curl \

docker/Dockerfile.ubuntu.xenial

@@ -14,6 +14,7 @@ RUN apt-get update && apt-get -y install \
   asn1c \
   automake \
   bison \
+  ccache \
   cmake \
   curl \
   e2fslibs-dev \