Mark two tests as unsupported on Windows for the moment

The IR patterns for COFF vs. ELF/MachO are annoying enough that will
need to have a separate test.

Author: DougGregor

test/IRGen/static-vtable-stubs.swift

@@ -8,6 +8,10 @@
 
 // REQUIRES: concurrency
 
+// Note: Windows uses internal linkage, which puts an extra step symbol before
+// _swift_dead_method_stub.
+// UNSUPPORTED: OS=windows-msvc
+
 //--- A.swift
 open class C {
   private var i: [ObjectIdentifier:Any] = [:]

test/IRGen/zombies.swift

@@ -1,5 +1,9 @@
 // RUN: %target-swift-frontend -primary-file %s -O -emit-ir | %FileCheck %s
 
+// Note: Windows uses internal linkage, which puts an extra step symbol before
+// _swift_dead_method_stub.
+// UNSUPPORTED: OS=windows-msvc
+
 // rdar://24121475
 //   Ideally, these wouldn't be in the v-table at all; but as long as they
 //   are, we need to emit symbols for them.