[gdk-pixbuf] build: Fix invalid syntax

[Bastien Nocera <hadess src gnome org>]

commit 8657c37443db3ca727c157666707052f3c9759b2
Author: Bastien Nocera <hadess hadess net>
Date:   Tue Sep 19 11:18:26 2017 +0200

    build: Fix invalid syntax
    
    WARNING: Passed invalid keyword argument "source" in gdk-pixbuf/meson.build line 243.

 gdk-pixbuf/meson.build |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gdk-pixbuf/meson.build b/gdk-pixbuf/meson.build
index b8889c0..77c162b 100644
--- a/gdk-pixbuf/meson.build
+++ b/gdk-pixbuf/meson.build
@@ -240,7 +240,7 @@ loaders_cache = custom_target('loaders.cache',
                                 dynamic_loaders,
                               ],
                               build_by_default: true)
-loaders_dep = declare_dependency(source: loaders_cache)
+loaders_dep = declare_dependency(sources: [ loaders_cache ])
 
 build_gir = get_option('with_gir') and not meson.is_cross_build()
 if build_gir