gitlab-ci: Move artifact preparation to separate script

It's currently only needed for the meson-main and meson-arm64 jobs, not
the other meson build jobs.

Also remove MESON_SHADERDB, just run .gitlab-ci/run-shader-db.sh
directly from the meson-main job.

v2:
* Also run prepare-artifacts.sh in meson-arm64 script
v3:
* Move tarball creation into the new script as well, as it prevented
  ccache --show-stats from running in after_script

Reviewed-by: Eric Engestrom <eric.engestrom@intel.com> # v1
Reviewed-by: Eric Anholt <eric@anholt.net>
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 2882e44..ceb78f3 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -161,12 +161,6 @@
     - ccache --zero-stats || true
     - ccache --show-stats || true
   after_script:
-    # In case the install dir is being saved as artifacts, tar it up
-    # so that symlinks and hardlinks aren't each packed separately in
-    # the zip file.
-    - if [ -d install ]; then
-        tar -cf artifacts/install.tar install;
-      fi
     - export CCACHE_DIR="$PWD/ccache"
     - ccache --show-stats
 
@@ -222,8 +216,11 @@
     EXTRA_OPTION: >
       -D osmesa=gallium
       -D tools=all
-    MESON_SHADERDB: "true"
     BUILDTYPE: "debugoptimized"
+  script:
+    - .gitlab-ci/meson-build.sh
+    - .gitlab-ci/run-shader-db.sh
+    - .gitlab-ci/prepare-artifacts.sh
 
 .meson-cross:
   extends:
@@ -270,6 +267,9 @@
     - .ci-deqp-artifacts
   variables:
     BUILDTYPE: "debugoptimized"
+  script:
+    - .gitlab-ci/meson-build.sh
+    - .gitlab-ci/prepare-artifacts.sh
 
 # NOTE: Building SWR is 2x (yes two) times slower than all the other
 # gallium drivers combined.