From a349a2f956bd7784b42ecbd5bdb46580def84563 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Sat, 16 May 2020 10:39:14 +1000
Subject: [PATCH] Tools: fixed SITL build

---
 Tools/ardupilotwaf/ap_library.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Tools/ardupilotwaf/ap_library.py b/Tools/ardupilotwaf/ap_library.py
index 1368d3c12f..e3e16cc38e 100644
--- a/Tools/ardupilotwaf/ap_library.py
+++ b/Tools/ardupilotwaf/ap_library.py
@@ -62,6 +62,8 @@ _depends_on_vehicle_cache = {}
 def _depends_on_vehicle(bld, source_node):
     path = source_node.srcpath()
 
+    if not bld.env.BUILDROOT:
+        bld.env.BUILDROOT = bld.bldnode.make_node('').abspath()
     if path.startswith(bld.env.BUILDROOT) or path.startswith("build/"):
         _depends_on_vehicle_cache[path] = False