testsuite: Prevent T16318 from picking up .ghci

Previously this test did nothing to prevent GHC from reading .ghci due
to the `-e` arguments. Consequently it could fail due to multiple
reloadings of DynFlags while evaluating .ghci.

testsuite/tests/driver/T16318/Makefile

@@ -6,6 +6,6 @@ test_pe = test-package-environment
 
 T16318:
 	"$(GHC_PKG)" latest base >  $(test_pe)
-	"$(TEST_HC)" $(TEST_HC_OPTS) -v1 -package-env $(test_pe) -e "putStrLn \"Hello\"" > out 2>&1
+	"$(TEST_HC)" $(TEST_HC_OPTS) -v1 -ignore-dot-ghci -package-env $(test_pe) -e "putStrLn \"Hello\"" > out 2>&1
 	C=`cat out | grep "Loaded package environment" -c` ; \
 	if [ $$C != "1" ]; then false; fi