ci: Use update_deps script in Travis-CI

Using the script causes CI to build the "known-good" versions of the
dependent repositories. This should improve the stability of the
CI testing of Vulkan-ValidationLayers.

If Travis CI is triggered by a cron job, it builds the master branch
of the dependent repositories.

Add Vulkan-Tools to "ci_only" repo list in known-good file since
the CI tests need the mock ICD.
diff --git a/scripts/known_good.json b/scripts/known_good.json
index 10c16be..e8dbe66 100644
--- a/scripts/known_good.json
+++ b/scripts/known_good.json
@@ -68,6 +68,27 @@
       "ci_only" : [
         "TRAVIS"
       ]
+    },
+    {
+      "name" : "Vulkan-Tools",
+      "url" : "https://github.com/KhronosGroup/Vulkan-Tools.git",
+      "sub_dir" : "Vulkan-Tools",
+      "build_dir" : "Vulkan-Tools/build",
+      "install_dir" : "Vulkan-Tools/build/install",
+      "commit" : "origin/sdk-1.1.77",
+      "deps" : [
+        {
+          "var_name" : "VULKAN_HEADERS_INSTALL_DIR",
+          "repo_name" : "Vulkan-Headers"
+        },
+        {
+          "var_name" : "VULKAN_LOADER_INSTALL_DIR",
+          "repo_name" : "Vulkan-Loader"
+        }
+      ],
+      "ci_only" : [
+        "TRAVIS"
+      ]
     }
   ],
   "install_names" : {