[PATCH 0/1] MR7688: Setupapi: Don't add backslash on absolute dirid

[Anders Kjersem (＠anders)]

The absolute dirid (-1) is an empty string and should not have a backslash appended to separate it from the filename; DestinationDirs with `-1` and a file spec like `c:\foo.bin` must remain as `c:\foo.bin` after `build_filepathsW`, it must not become `\c:\foo.bin`. This also fixes a undefined access to `buffer[-1]` when src2 is an empty string!