clang/test/CodeGenCXX/debug-info-namespace.cpp: Suppress this also on msys, for now since r193116.

Clang confuses among dosish paths. In this case, "Input/foo.cpp" and "Input\foo.cpp" cannot be unified.

llvm-svn: 193456
diff --git a/clang/test/CodeGenCXX/debug-info-namespace.cpp b/clang/test/CodeGenCXX/debug-info-namespace.cpp
index 6932120..a2d7ede 100644
--- a/clang/test/CodeGenCXX/debug-info-namespace.cpp
+++ b/clang/test/CodeGenCXX/debug-info-namespace.cpp
@@ -74,3 +74,4 @@
 
 // FIXME: It is confused on win32 to generate file entry when dosish filename is given.
 // REQUIRES: shell
+// REQUIRES: shell-preserves-root