[Test] Check imported enum is BC.

Author: nate-chandler

test/Sema/bitwse_copyable_import.swift

@@ -60,6 +60,11 @@ struct IntsTrailing3 {
   int is[];
 } __attribute__((__swift_attr__("_BitwiseCopyable")));
 
+enum E {
+  foo,
+  bar
+};
+
 //--- Downstream.swift
 
 func take<T : _BitwiseCopyable>(_ t: T) {}
@@ -85,3 +90,7 @@ func passIntsTrailing2(_ t: IntsTrailing2) {
 func passIntsTrailing3(_ t: IntsTrailing3) {
   take(t)
 }
+
+func passE(_ e: E) {
+  take(e)
+}