[gimp] gitlab-ci: libspiro is needed to run `gegl`.

[Jehan <jehanp src gnome org>]

commit 60854c86684e0a488e94823ab78e015c7649aa12
Author: Jehan <jehan girinstud io>
Date:   Mon Apr 13 14:22:45 2020 +0200

    gitlab-ci: libspiro is needed to run `gegl`.
    
    `gegl` binary is being run for icon generations on gimp-2-10.
    
    (cherry picked from commit 97549081fd535e1a801dbd37c3b9c1d6ffea50ba)
    
    Note: this commit is so far not needed on master as we don't call gegl
    during build time unlike in gimp-2-10. But we could at some point.
    Better to be thorough.

 .gitlab-ci.yml | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 0de76f8c41..917aaea163 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -107,6 +107,7 @@ deps-debian/testing:
         libpoppler-glib-dev
         libraw19
         librsvg2-dev
+        libspiro-dev
         libtiff-dev
         libtool
         libumfpack5