[gtksourceview: 1/2] meson: Use gnome.post_install() when meson is recent enough

[Christian Hergert <chergert src gnome org>]

commit 16c03594d6ed53c5c8979e694e1adb8da60ea41a
Author: Xavier Claessens <xavier claessens collabora com>
Date:   Mon Mar 8 22:06:56 2021 -0500

    meson: Use gnome.post_install() when meson is recent enough
    
    It has the advantage of working when gtk4 is built as a subproject.

 meson.build | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index b655259b..b9976b5c 100644
--- a/meson.build
+++ b/meson.build
@@ -337,4 +337,10 @@ summary = [
 
 message('\n'.join(summary))
 
-meson.add_install_script('meson_postinstall.py')
+if meson.version().version_compare('>=0.57.0')
+  gnome.post_install(
+    gtk_update_icon_cache: true,
+  )
+else
+  meson.add_install_script('meson_postinstall.py')
+endif