fix ccache for Docker images

.ci/travis/linux/script.sh

@@ -19,12 +19,13 @@ set -e
 mkdir -p "$CCACHE_DIR"
 
 if [[ ${DOCKER_BUILD_QGIS_IMAGE} =~ true ]]; then
+  # copy ccache dir within QGIS source so it can be accessed from docker
+  cp -r ${CCACHE_DIR} ${TRAVIS_BUILD_DIR}/.ccache
   # building docker images
   DIR=$(git rev-parse --show-toplevel)/.docker
   pushd "${DIR}"
   echo "${bold}Building QGIS Docker image '${DOCKER_TAG}'...${endbold}"
-  docker build --build-arg CACHE_DIR=/root/.ccache \
-               --build-arg DOCKER_TAG="${DOCKER_TAG}" \
+  docker build --build-arg DOCKER_TAG="${DOCKER_TAG}" \
                --cache-from "qgis/qgis:${DOCKER_TAG}" \
                -t "qgis/qgis:${DOCKER_TAG}" \
                -f qgis.dockerfile ..

.docker/docker-compose.travis.yml

@@ -16,7 +16,7 @@ services:
     image: qgis/qgis3-build-deps:${DOCKER_TAG}
     volumes:
       - ${TRAVIS_BUILD_DIR}:/root/QGIS
-      - $HOME/.ccache:/root/.ccache  # if changed, also change env var
+      - ${CCACHE_DIR}:/root/.ccache  # if changed, also change env var
     links:
       - postgres
       - mssql

.docker/qgis.dockerfile

@@ -3,14 +3,12 @@
 # see https://docs.docker.com/docker-cloud/builds/advanced/
 # using ARG in FROM requires min v17.05.0-ce
 ARG DOCKER_TAG=latest
-ARG CACHE_DIR
 
 FROM  qgis/qgis3-build-deps:${DOCKER_TAG}
 MAINTAINER Denis Rouzaud <denis@opengis.ch>
 
 LABEL Description="Docker container with QGIS" Vendor="QGIS.org" Version="1.1"
 
-
 ENV CC=/usr/lib/ccache/clang
 ENV CXX=/usr/lib/ccache/clang++
 ENV QT_SELECT=5
@@ -18,8 +16,7 @@ ENV LANG=C.UTF-8
 
 COPY . /usr/src/QGIS
 
-COPY ${CACHE_DIR} /root/.ccache
-ENV CCACHE_DIR=/root/.ccache
+ENV CCACHE_DIR=/usr/src/QGIS/.ccache
 RUN ccache -M 1G
 RUN ccache -s
 

.travis.yml

@@ -7,7 +7,7 @@ cache:
   apt: true
   pip: true
   directories:
-    - $HOME/.ccache
+    - ${HOME}/.ccache
   timeout: 1000
 
 env: