[gedit] build: simplify instructions for the AppData

[Sébastien Wilmet <swilmet src gnome org>]

commit ba307433b78dd1282a90e01ab685eaf7d22023ab
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Wed Dec 4 17:20:40 2019 +0100

    build: simplify instructions for the AppData
    
    - The type xml is the default.
    - po_dir: the documentation says that it needs to be a relative path.
    - Avoid using the datadir global variable.

 data/meson.build | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)
---
diff --git a/data/meson.build b/data/meson.build
index c9f152047..00cdaa10a 100644
--- a/data/meson.build
+++ b/data/meson.build
@@ -2,17 +2,14 @@ subdir('icons')
 
 install_man('gedit.1')
 
+appdata = 'org.gnome.gedit.appdata.xml'
 appdata_file = i18n.merge_file(
-  'appdata-file',
-  input: 'org.gnome.gedit.appdata.xml.in',
-  output: 'org.gnome.gedit.appdata.xml',
-  type: 'xml',
-  po_dir: join_paths(srcdir, 'po'),
+  appdata,
+  input: appdata + '.in',
+  output: appdata,
+  po_dir: '../po/',
   install: true,
-  install_dir: join_paths(
-    datadir,
-    'metainfo',
-  )
+  install_dir: join_paths(get_option('prefix'), get_option('datadir'), 'metainfo')
 )
 
 appstream_util = find_program('appstream-util', required: false)