Index: llvm/utils/lit/tests/lit.cfg
===================================================================
--- llvm/utils/lit/tests/lit.cfg
+++ llvm/utils/lit/tests/lit.cfg
@@ -53,7 +53,7 @@
     config.test_source_root, 'Inputs')))
 config.substitutions.append(('%{lit}',
     "{env} %{{python}} {lit}".format(
-        env="env -u FILECHECK_OPTS -u FILECHECK_DUMP_INPUT_ON_FAILURE",
+        env="env FILECHECK_OPTS= FILECHECK_DUMP_INPUT_ON_FAILURE=",
         lit=os.path.join(lit_path, 'lit.py'))))
 config.substitutions.append(('%{python}', '"%s"' % (sys.executable)))