[TypeChecker] NFC: Restrict executable test for type inference from defaults to macOS

Author: xedin

test/Constraints/type_inference_from_default_exprs_executable_test.swift

@@ -3,6 +3,8 @@
 // RUN: %target-build-swift -module-name main -Xfrontend -enable-experimental-type-inference-from-defaults -parse-as-library -I %t %s %S/Inputs/type_inference_via_defaults_other_module.swift -o %t/a.out
 // RUN: %target-run %t/a.out | %FileCheck %s --color
 
+// REQUIRES: OS=macosx
+
 protocol P {
   associatedtype X
 }