[embedded] Mark test as unsupported on Windows.

Author: zoecarver

test/embedded/basic-irgen-no-stdlib.swift

@@ -1,5 +1,8 @@
 // RUN: %target-swift-emit-ir %s -parse-stdlib -enable-experimental-feature Embedded -target arm64e-apple-none | %FileCheck %s
 
+// TODO: investigate why windows is generating more metadata.
+// XFAIL: OS=windows-msvc
+
 struct Bool {}
 
 protocol Player {