--- b/SConstruct	2018-07-03 23:13:51.986746857 +0200
+++ a/SConstruct	2018-07-03 23:14:50.495252914 +0200
@@ -221,7 +221,7 @@
     'STAGING_PREFIX',  # Required by the OpenWRT and CeroWrt builds.
     'WRITE_PAD',       # So we can test WRITE_PAD values on the fly.
     )
-envs = {}
+envs = os.environ
 for var in import_env:
     if var in os.environ:
         envs[var] = os.environ[var]