+# Propagate 'INCLUDE' through the environment.
+if 'INCLUDE' in os.environ:
+ config.environment['INCLUDE'] = os.environ['INCLUDE']
+
+# Propagate 'LIB' through the environment.
+if 'LIB' in os.environ:
+ config.environment['LIB'] = os.environ['LIB']
+
+# Propagate LLVM_SRC_ROOT into the environment.