build: Use GNOME module post_install()

This greatly simplifies the post install script. As this functionality
depends on newer meson (0.59.0) it is guarded by a version check.
Distributions usually use their own tooling so it's does not matter if
they don't run the postinstall scripts (e.g. because of using too old
meson)

build-aux/meson/postinstall.py

@@ -1,18 +0,0 @@
-#!/usr/bin/env python3
-
-from os import environ, path
-from subprocess import call
-
-# Package managers set this, so we don't need to run
-if not environ.get('DESTDIR', ''):
-    prefix = environ.get('MESON_INSTALL_PREFIX', '/usr/local')
-    datadir = path.join(prefix, 'share')
-
-    print('Updating icon cache...')
-    call(['gtk-update-icon-cache', '-qtf', path.join(datadir, 'icons', 'hicolor')])
-
-    print('Updating desktop database...')
-    call(['update-desktop-database', path.join(datadir, 'applications')])
-
-    print('Compiling schemas...')
-    call(['glib-compile-schemas', path.join(datadir, 'glib-2.0', 'schemas')])

meson.build

@@ -137,4 +137,14 @@ subdir('plugins')
 subdir('doc')
 subdir('data')
 
-meson.add_install_script('build-aux/meson/postinstall.py')
+# gnome.post_install() is available since meson 0.59.0
+# Distributions use their own tooling (e.g. postinst, triggers, etc)
+# so it is okay if the post_install() is not run on distro builds
+m_ver = meson.version().split('.')
+if m_ver[0].to_int() > 0 or m_ver[1].to_int() > 58
+  gnome.post_install(
+    glib_compile_schemas: true,
+    gtk_update_icon_cache: true,
+    update_desktop_database: true,
+  )
+endif