[libsoup] meson: Fix the generated vapi file

[Tomas Popela <tpopela src gnome org>]

commit f58dd87267423aeaa89b4a7c09baee029d7c6a28
Author: Tomas Popela <tpopela redhat com>
Date:   Fri Sep 7 07:21:31 2018 +0200

    meson: Fix the generated vapi file
    
    Include the custom.vala file while generating the vapi file.
    
    Closes: #13

 libsoup/meson.build | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
---
diff --git a/libsoup/meson.build b/libsoup/meson.build
index 149c5c21..2b149a0e 100644
--- a/libsoup/meson.build
+++ b/libsoup/meson.build
@@ -311,8 +311,13 @@ if enable_introspection or enable_vapi
     sources : soup_gir_gen_sources)
 
   if enable_vapi
+    soup_ns_version = '@0@-@1@'.format(soup_ns, apiversion)
+
     gnome.generate_vapi(libsoup_api_name,
-      sources : soup_gir_gen_sources[0],
+      sources : [
+        soup_gir_gen_sources[0],
+        soup_ns_version + '-custom.vala'
+      ],
       packages : 'gio-2.0',
       install : true,
     )