[gnome-system-monitor] Use meson-provided gnome post-install

[Robert Roth <robertroth src gnome org>]

commit b2ce7b3ac76f9e51633aea75d7fddf6ee31d4e4a
Author: Robert Roth <robert roth off gmail com>
Date:   Sun Mar 6 08:22:12 2022 +0200

    Use meson-provided gnome post-install

 meson.build           |  8 ++++++--
 meson_post_install.py | 17 -----------------
 2 files changed, 6 insertions(+), 19 deletions(-)
---
diff --git a/meson.build b/meson.build
index dd70c427..426a8aa7 100644
--- a/meson.build
+++ b/meson.build
@@ -10,7 +10,7 @@ project('gnome-system-monitor',
     'libhandy:tests=false',
   ],
   version: '42.beta',
-  meson_version: '>=0.50.0',
+  meson_version: '>=0.57.0',
 )
 
 
@@ -205,4 +205,8 @@ message('\n'.join(['',
       libwnck.found() ? '(this will likely make system-monitor segfault)' : ''),
 ]))
 
-meson.add_install_script('meson_post_install.py')
+# Extra scripts
+gnome.post_install(
+  glib_compile_schemas: true,
+  gtk_update_icon_cache: true,
+)