[gnome-build-meta/matthiasc/3.38.4] Switch gtkmm to meson

[Matthias Clasen <matthiasc src gnome org>]

commit 55615e34a485384e2fdf6573980bcb05ef243120
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Feb 16 16:33:41 2021 -0500

    Switch gtkmm to meson
    
    the autotools build seems to have decayed.

 elements/core-deps/gtkmm-3.bst | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)
---
diff --git a/elements/core-deps/gtkmm-3.bst b/elements/core-deps/gtkmm-3.bst
index e04eb768..22228858 100644
--- a/elements/core-deps/gtkmm-3.bst
+++ b/elements/core-deps/gtkmm-3.bst
@@ -1,4 +1,4 @@
-kind: autotools
+kind: meson
 sources:
 - kind: tar
   url: gnome_downloads:gtkmm/3.24/gtkmm-3.24.3.tar.xz
@@ -13,6 +13,3 @@ depends:
 - sdk/glib.bst
 - sdk/gtk+-3.bst
 - freedesktop-sdk.bst:bootstrap-import.bst
-variables:
-  conf-local: >-
-    --enable-maintainer-mode