gitlab-ci: Use meson buildtype debug instead of default debugoptimized

This can save a lot of time for some of the meson CI jobs.

Acked-by: Eric Engestrom <eric.engestrom@intel.com>

.gitlab-ci.yml

@@ -94,6 +94,7 @@ debian:
     - meson --version
     - meson _build
             --native-file=native.file
+            -D buildtype=debug
             -D build-tests=true
             -D libunwind=${UNWIND}
             ${DRI_LOADERS}