Add Requires line to test.

Author: davidungar

test/Frontend/immediate-mode-no-output.swift

@@ -1,3 +1,4 @@
+// REQUIRES: swift_interpreter
 // RUN: %empty-directory(%t)
 // RUN: cd %t && %target-swift-frontend -interpret %S/../Inputs/empty.swift
 // RUN: not ls %t/*