[clang] Make test separator-agnostic

Author: jansvoboda11

clang/test/Modules/module-debuginfo-prefix.m

@@ -23,4 +23,4 @@
 
 // Dir should always be empty, but on Windows we can't recognize /var
 // as being an absolute path.
-// CHECK: !DIFile(filename: "/OVERRIDE/DebugObjC.h", directory: "{{()|(.*:.*)}}")
+// CHECK: !DIFile(filename: "/OVERRIDE{{/|\\\\?}}DebugObjC.h", directory: "{{()|(.*:.*)}}")