[gtkmm] CI: Install modules required for building gtk4

[Kjell Ahlstedt <kjellahl src gnome org>]

commit fc34b61ffa17e343ed0108614932ab0422aa29ca
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Wed Feb 9 16:39:35 2022 +0100

    CI: Install modules required for building gtk4
    
    If the gtk4 version in ubuntu:devel is too old, gtk4 is built as
    a subproject to gtkmm.

 .gitlab-ci.yml | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index b362a209..e2aaa2d4 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -24,6 +24,13 @@ variables:
                   meson
                   ninja-build
                   glib-networking
+
+  # If libgtk-4-dev is too old, gtk4 is built as a subproject to gtkmm-4.0.
+  GTK4_BUILD_DEPS: libgstreamer1.0-dev
+                   libgstreamer-plugins-base1.0-dev
+                   libgstreamer-plugins-good1.0-dev
+                   libgstreamer-plugins-bad1.0-dev
+                   libgudev-1.0-dev
   GIO_EXTRA_MODULES: "/usr/lib/x86_64-linux-gnu/gio/modules"
   GIT_SUBMODULE_STRATEGY: normal
 
@@ -106,7 +113,7 @@ release_gcc_build:
   extends: .build_default
   stage: build
   variables:
-    DEPENDENCIES: $MESON_GCC_DEPS
+    DEPENDENCIES: $MESON_GCC_DEPS $GTK4_BUILD_DEPS
   script:
     - ninja -C libsigc/_build install
     - ninja -C glibmm/_build install
@@ -141,7 +148,7 @@ release_clang_build:
   extends: .build_default
   stage: build
   variables:
-    DEPENDENCIES: $MESON_GCC_DEPS clang
+    DEPENDENCIES: $MESON_GCC_DEPS $GTK4_BUILD_DEPS clang
   script:
     - ninja -C libsigc/_build install
     - ninja -C glibmm/_build install