[json-glib] docs Use the relative location of the sources

[Emmanuele Bassi <ebassi src gnome org>]

commit 71d8451659600a67bcdd5524b9e6eedf0e7ff354
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Mon Aug 24 18:32:59 2020 +0100

    docs Use the relative location of the sources
    
    Do not use source_root()/build_root(), as they prevent building
    json-glib as a sub-project.

 doc/meson.build | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)
---
diff --git a/doc/meson.build b/doc/meson.build
index edee3a4..8f27ff6 100644
--- a/doc/meson.build
+++ b/doc/meson.build
@@ -23,10 +23,7 @@ if find_program('gtkdoc-scan', required : get_option('gtk_doc')).found()
   gnome.gtkdoc(
     'json-glib',
     main_xml: 'json-glib-docs.xml',
-    src_dir: [
-      join_paths(meson.source_root(), 'json-glib'),
-      join_paths(meson.build_root(), 'json-glib'),
-    ],
+    src_dir: include_directories('../json-glib'),
     dependencies: json_glib_dep,
     gobject_typesfile: 'json-glib.types',
     scan_args: [