[ThinLTO] XFAIL path manipulation test on Windows

This test is creating and checking paths using '/'. XFAIL it on Windows
to unbreak bot:
http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-windows10pro-fast/builds/5478

llvm-svn: 269775
diff --git a/llvm/test/ThinLTO/X86/prefix_replace.ll b/llvm/test/ThinLTO/X86/prefix_replace.ll
index 7ae7d35..b378a58 100644
--- a/llvm/test/ThinLTO/X86/prefix_replace.ll
+++ b/llvm/test/ThinLTO/X86/prefix_replace.ll
@@ -1,4 +1,6 @@
 ; Check that changing the output path via prefix-replace works
+; Use of '/' in paths created here make this unsuitable for Windows.
+; XFAIL: win32
 ; RUN: mkdir -p %T/oldpath
 ; RUN: opt -module-summary %s -o %T/oldpath/prefix_replace.o
 ; Ensure that there is no existing file at the new path, so we properly