[gnome-build-meta] Switch wayland to build from tarball

[Michael Catanzaro <mcatanzaro src gnome org>]

commit dc6bb6246e66bffc94ac53b839766cc5800a679f
Author: Michael Catanzaro <mcatanzaro igalia com>
Date:   Tue Jun 19 17:20:33 2018 -0500

    Switch wayland to build from tarball
    
    tarball-conversion is failing because
    https://wayland.freedesktop.org/releases is now a GitLab 404 page.

 elements/core-deps/wayland.bst | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)
---
diff --git a/elements/core-deps/wayland.bst b/elements/core-deps/wayland.bst
index eb7cf2f..0ac9b71 100644
--- a/elements/core-deps/wayland.bst
+++ b/elements/core-deps/wayland.bst
@@ -1,8 +1,7 @@
 kind: autotools
 sources:
-- kind: git
-  url: git_freedesktop_org:wayland/wayland
-  track: master
+- kind: tar
+  url: https://wayland.freedesktop.org/releases/wayland-1.15.0.tar.xz
 depends:
 - filename: base.bst
   junction: freedesktop-sdk.bst