Index: test/FileCheck/lit.local.cfg
===================================================================
--- /dev/null
+++ test/FileCheck/lit.local.cfg
@@ -0,0 +1,13 @@
+# Unset environment variables that the FileCheck tests
+# expect not to be set.
+file_check_expected_unset_vars = [
+  'FILECHECK_DUMP_INPUT_ON_FAILURE',
+  'FILECHECK_OPTS',
+]
+
+for env_var in file_check_expected_unset_vars:
+  if env_var in config.environment:
+    lit_config.note('Removing {} from environment for FileCheck tests'.format(
+      env_var)
+    )
+    config.environment.pop(env_var)