[recipes] Try to fix meson build in flatpak

[Matthias Clasen <matthiasc src gnome org>]

commit dfe4baedb36247600058886c2099405581ab074d
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Feb 21 20:35:53 2017 -0500

    Try to fix meson build in flatpak
    
    We can't let meson use git at build time, since we don't
    have network access at that time, when building a flatpak.
    
    Instead, add it as a submodule.

 .gitmodules            |    3 +++
 subprojects/libgd      |    1 +
 subprojects/libgd.wrap |    4 ----
 3 files changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/.gitmodules b/.gitmodules
index bfd964e..5deb59b 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +1,6 @@
 [submodule "libgd"]
        path = libgd
        url = git://git.gnome.org/libgd
+[submodule "subprojects/libgd"]
+       path = subprojects/libgd
+       url = git://git.gnome.org/libgd
diff --git a/subprojects/libgd b/subprojects/libgd
new file mode 160000
index 0000000..3566de0
--- /dev/null
+++ b/subprojects/libgd
@@ -0,0 +1 @@
+Subproject commit 3566de04a1da644a4b88266e7cfee58d70ee1fac