[geary] meson: Use gnome.post_install

[Niels De Graef <nielsdg src gnome org>]

commit 146a76c0ddd2787b5a3131e6ab6394ec851445bb
Author: Maximiliano Sandoval R <msandova gnome org>
Date:   Fri Mar 18 12:18:59 2022 +0100

    meson: Use gnome.post_install
    
    Requires meson 0.59. The command to update the desktop database was not
    executed which could lead to the app not appearing on the apps menu
    after install.

 build-aux/post_install.py | 15 ---------------
 meson.build               |  8 ++++++--
 2 files changed, 6 insertions(+), 17 deletions(-)
---
diff --git a/meson.build b/meson.build
index 94e0eda32..a2cde71b0 100644
--- a/meson.build
+++ b/meson.build
@@ -221,8 +221,12 @@ endif
 
 files(iso_639_xml, iso_3166_xml) # Check to make sure these exist
 
-# Post-install scripts
-meson.add_install_script('build-aux' / 'post_install.py')
+# Post-install script
+gnome.post_install(
+  gtk_update_icon_cache: true,
+  glib_compile_schemas: true,
+  update_desktop_database: true,
+)
 
 # Subfolders
 subdir('desktop')