Gitlab-CI: Handle ccache path correctly and sync upstream Salsa-CI changes

Salsa-CI changed the path names of .ccache and thus MariaDB builds stopped
working as the file size of the artifact directory with .ccache included
was way over limits. These changes put the .ccache directory in the correct
place and slims down the amount of total artifacts.

debian/gitlab-ci.yml

@@ -7,8 +7,6 @@ include:
 variables:
   DEB_BUILD_OPTIONS: "nocheck noautodbgsym"
   RELEASE: stretch
-  CCACHE_TMP_DIR: ${CI_PROJECT_DIR}/../.ccache
-  CCACHE_WORK_DIR: ${WORKING_DIR}/.ccache
   SALSA_CI_DISABLE_REPROTEST: 1
 
 stages:
@@ -23,8 +21,11 @@ stages:
 build:
   extends: .build-package
   script:
-    - apt-get update
-    - mkdir -p ${CCACHE_WORK_DIR}
+    # salsa-ci-team/pipeline#104
+    - rm -rf '$CI_PROJECT_DIR'
+    # salsa-ci-team/pipeline#107
+    - rm -rf ${CI_PROJECT_DIR}/debian/output/.ccache
+    - mkdir -p ${WORKING_DIR} ${CCACHE_WORK_DIR}
     - mv ${CCACHE_WORK_DIR} ${CCACHE_TMP_DIR}
     - gbp pull --ignore-branch --pristine-tar --track-missing
     - |