Fix Gitlab cache issues (#3160)

* Make parent cache download quiet

This spammed logs quite a bit

* Add "-p" to "mkdir $CI_PROJECT_DIR/cache-artifact"

Otherwise the after_script is silently aborted when the dir already exists.

* Extract parent cache artifact in own directory and later delete it

Otherwise we end up having "testlogs" (and maybe other stuff) in the
project directory, which causes future failures.

.gitlab-ci.yml

@@ -33,13 +33,17 @@ stages:
       if [ "$CI_COMMIT_REF_SLUG" != "develop" -a "$CI_COMMIT_TAG" == "" ]; then
         if [ ! -d $CACHE_DIR/ccache ]; then
           echo "Downloading cache from develop branch"
-          if wget -O cache-artifact.zip https://gitlab.com/$CI_PROJECT_NAMESPACE/$CI_PROJECT_NAME/-/jobs/artifacts/develop/download?job=$CI_JOB_NAME; then
-            unzip cache-artifact.zip
+          mkdir cache-artifact
+          cd cache-artifact
+          if wget --quiet -O cache-artifact.zip https://gitlab.com/$CI_PROJECT_NAMESPACE/$CI_PROJECT_NAME/-/jobs/artifacts/develop/download?job=$CI_JOB_NAME; then
+            unzip -q cache-artifact.zip
             rm cache-artifact.zip
             mv cache-artifact/* $CACHE_DIR/
           else
             echo "Failed to download cache"
           fi
+          cd ..
+          rm -rf cache-artifact
         else
           echo "Not touching cache (was initialized from previous build)"
         fi
@@ -97,7 +101,7 @@ stages:
   after_script:
     # Copy all cache files into cache-artifact so that they get uploaded. We only do this for develop so that artifacts
     # stay minimal for PRs and branches (we never need them)
-    - mkdir $CI_PROJECT_DIR/cache-artifact
+    - mkdir -p $CI_PROJECT_DIR/cache-artifact
     - mkdir -p $CI_PROJECT_DIR/testlogs
     - |
       if [ "$CI_COMMIT_REF_SLUG" = "develop" ]; then