tests: fix the requirements for embedded/unowned-task-executor.swift

rdar://157120950

Author: eeckstein

test/embedded/unowned-task-executor.swift

@@ -1,5 +1,8 @@
 // RUN: %target-swift-frontend -enable-experimental-feature Embedded -disable-availability-checking -module-name test -parse-as-library %s -emit-ir | %FileCheck %s
 
+// REQUIRES: executable_test
+// REQUIRES: swift_in_compiler
+// REQUIRES: optimized_stdlib
 // REQUIRES: OS=macosx
 // REQUIRES: swift_feature_Embedded