[gtk] Bump meson req to 0.50

[Matthias Clasen <matthiasc src gnome org>]

commit f0845d98a21a7a5c5817d50f2076dd2615e3979b
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Mar 28 17:35:50 2019 -0400

    Bump meson req to 0.50
    
    meson told me to.

 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index 5ce18aaa0b..7319640b10 100644
--- a/meson.build
+++ b/meson.build
@@ -7,7 +7,7 @@ project('gtk', 'c',
           # https://github.com/mesonbuild/meson/issues/2289
           'c_std=gnu99',
         ],
-        meson_version : '>= 0.48.0',
+        meson_version : '>= 0.50.0',
         license: 'LGPLv2.1+')
 
 glib_major_req = 2