Write out the \c CXVirtualFileOverlay object to a char buffer.
\param options is reserved, always pass 0.
\param out_buffer_ptr pointer to receive the buffer pointer, which should be
disposed using \c clang_free().
\param out_buffer_size pointer to receive the buffer size.
\returns 0 for success, non-zero to indicate an error.
Write out the \c CXVirtualFileOverlay object to a char buffer.
\param options is reserved, always pass 0. \param out_buffer_ptr pointer to receive the buffer pointer, which should be disposed using \c clang_free(). \param out_buffer_size pointer to receive the buffer size. \returns 0 for success, non-zero to indicate an error.