Clang: Handle native file in the file cache

Different types are introduced for normalized and native file path. So the
compiler is warning you if you try the wrong format.

Change-Id: I1da0686b142cbf9bb7578468c2b50f90a94cebf9
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/tools/clangrefactoringbackend/source/clangtool.h

@@ -63,7 +63,7 @@ struct FileContent
                 const std::vector<std::string> &commandLine)
         : directory(directory),
           fileName(fileName),
-          filePath(directory + nativeSeperator + fileName),
+          filePath(directory + nativeSeparator + fileName),
           content(content),
           commandLine(commandLine)
     {}