[gimp/wip/Jehan/CI-Windows: 3/4] gitlab-ci: move to debian testing image as base.

[Jehan <jehanp src gnome org>]

commit e95b20eac99c03c9bbda28c05098624d8620b5f8
Author: Jehan <jehan girinstud io>
Date:   Wed Sep 25 21:34:45 2019 +0200

    gitlab-ci: move to debian testing image as base.
    
    It looks like Arch does not have mingw64 cross-compilers in core package
    repository. It does have some package in the user repository (AUR), but
    I assume that such a repository cannot be deemed as safe.
    
    Anyway I still tried, but apparently these AUR packages have to be built
    and when I tried, I got this error:
    >  ERROR: Running makepkg as root is not allowed as it can cause
    > permanent, catastrophic damage to your system.
    (I was not even running anything as root, does it mean that any command
    run inside the CI system is run as root by default?)
    
    Anyway it's all a big mess. So this is my attempt to move to Debian
    testing, which is anyway our base compatibility system.

 .gitlab-ci.yml | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 6952dd5bb1..438bef546c 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,4 +1,4 @@
-image: salamandar/archlinux-gimp:latest
+image: debian:testing
 
 stages:
   - gimp
@@ -6,12 +6,10 @@ stages:
 variables:
   INSTALL_DIR: "_install"
   INSTALL_PREFIX: "${CI_PROJECT_DIR}/${INSTALL_DIR}"
-  PACMAN_CACHE:   "${CI_PROJECT_DIR}/_pacman_cache"
 
 cache:
   paths:
-  - _pacman_cache
-
+  - /var/cache/apt
 
 # build-min-autotools:
 #   extends: .gimp-autotools