[mutter] build: Add postinstall script

[Jonas Ådahl <jadahl src gnome org>]

commit ccefa8735130a05eaf3e3555a6044f22b9aebc09
Author: Florian Müllner <fmuellner gnome org>
Date:   Tue Aug 27 12:30:14 2019 +0300

    build: Add postinstall script
    
    ... to compile schemas and update the desktop database when installing
    from source rather than building a distribution package.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/756

 meson.build                |  2 ++
 meson/meson-postinstall.sh | 10 ++++++++++
 2 files changed, 12 insertions(+)
---
diff --git a/meson.build b/meson.build
index b76ce915b..6160a4bb3 100644
--- a/meson.build
+++ b/meson.build
@@ -404,6 +404,8 @@ subdir('src')
 subdir('po')
 subdir('doc/man')
 
+meson.add_install_script('meson/meson-postinstall.sh')
+
 output = [
   '',
   '',
diff --git a/meson/meson-postinstall.sh b/meson/meson-postinstall.sh
new file mode 100755
index 000000000..4500dcb01
--- /dev/null
+++ b/meson/meson-postinstall.sh
@@ -0,0 +1,10 @@
+#!/bin/sh
+
+# Package managers set this so we don't need to run
+if [ -z "$DESTDIR" ]; then
+  echo Compiling GSettings schemas...
+  glib-compile-schemas ${MESON_INSTALL_PREFIX}/share/glib-2.0/schemas
+
+  echo Updating desktop database...
+  update-desktop-database -q ${MESON_INSTALL_PREFIX}/share/applications
+fi