Revert "Fix path separator issue on Windows."

This reverts commit 9242ff16b0460b488691fd70b42a2bf81a531e3a.

llvm-svn: 236806

clang/lib/Lex/HeaderSearch.cpp

@@ -614,8 +614,10 @@ const FileEntry *HeaderSearch::LookupFile(
       const FileEntry *Includer = IncluderAndDir.first;
 
       // Concatenate the requested file onto the directory.
+      // FIXME: Portability.  Filename concatenation should be in sys::Path.
       TmpDir = IncluderAndDir.second->getName();
-      llvm::sys::path::append(TmpDir, Filename);
+      TmpDir.push_back('/');
+      TmpDir.append(Filename.begin(), Filename.end());
 
       // FIXME: We don't cache the result of getFileInfo across the call to
       // getFileAndSuggestModule, because it's a reference to an element of