MoltenVK: Add patch to turn on framebuffer fetch in SPIRV-Cross

Externals/MoltenVK/patch.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+# Applies all patches in the "patches" folder to the cloned MoltenVK git repository.
+#
+# Usage: patch.sh <patches folder> <MoltenVK version>
+#
+
+set -e
+
+# Reset the git repository first to ensure that it's in the base state.
+git reset --hard $2
+
+git apply $1/*.patch