Add recipe support.

recipes/VulkanHeaders/recipe.py

@@ -0,0 +1,9 @@
+
+import os
+from SCons.Script import *
+
+def cook(env: Environment, git_ref: str = "main") -> dict:
+    repo = env.Cook('GitBranch', repo_name = 'VulkanHeaders', remote_url = 'https://github.com/KhronosGroup/Vulkan-Headers.git', git_ref = git_ref)
+    checkout_root = repo['checkout_root']
+    env.Append(CPPPATH = [os.path.join(checkout_root, 'include')])
+    return {}