[Test] Add test for crash while emitting reference dependencies.

This bug was fixed as part of the rework of our handling of
closure/local discriminators with respect to macros, but add a test
case to ensure that we don't regress. Tracked by rdar://108300632.

Author: DougGregor

test/Macros/macro_expand.swift

@@ -24,7 +24,7 @@
 // RUN: %target-swift-frontend -swift-version 5 -emit-ir -load-plugin-library %t/%target-library-name(MacroDefinition) %s -module-name MacroUser -o - -g | %FileCheck --check-prefix CHECK-IR %s
 
 // Execution testing
-// RUN: %target-build-swift -swift-version 5 -g -load-plugin-library %t/%target-library-name(MacroDefinition) %s -o %t/main -module-name MacroUser
+// RUN: %target-build-swift -swift-version 5 -g -load-plugin-library %t/%target-library-name(MacroDefinition) %s -o %t/main -module-name MacroUser -Xfrontend -emit-dependencies-path -Xfrontend %t/main.d -Xfrontend -emit-reference-dependencies-path -Xfrontend %t/main.swiftdeps
 // RUN: %target-codesign %t/main
 // RUN: %target-run %t/main | %FileCheck %s