[gnome-sdk-images] gtk3: Make the immodules path writable

[Mathieu Bridon <mbridon src gnome org>]

commit d51e4f82ca6b78400081b2495244240c4fc3e1a2
Author: Mathieu Bridon <bochecha daitauha fr>
Date:   Sat May 27 12:59:00 2017 +0200

    gtk3: Make the immodules path writable
    
    The build started failing without this:
    
    http://sdkbuilder1.gnome.org//logs/build-2017-05-27-082046/build-gnome-sdk-images-master-x86_64.txt

 org.gnome.Sdk.json.in |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/org.gnome.Sdk.json.in b/org.gnome.Sdk.json.in
index 659fe8e..e254459 100644
--- a/org.gnome.Sdk.json.in
+++ b/org.gnome.Sdk.json.in
@@ -395,6 +395,7 @@
                 "/bin/gtk-builder-tool",
                 "/bin/gtk-encode-symbolic-svg"
             ],
+            "ensure-writable": ["/lib/gtk-3.0/*/immodules.cache"],
             "sources": [
                 {
                     "type": "git",