--- modules/squish/SCsub.orig	2018-06-13 12:02:27 UTC
+++ modules/squish/SCsub
@@ -23,7 +23,7 @@ if env['builtin_squish']:
     thirdparty_sources = [thirdparty_dir + file for file in thirdparty_sources]
 
     env_squish.add_source_files(env.modules_sources, thirdparty_sources)
-    env_squish.Append(CPPPATH=[thirdparty_dir])
+    env_squish.Prepend(CPPPATH=[thirdparty_dir])
 
 # Godot source files
 env_squish.add_source_files(env.modules_sources, "*.cpp")