canonicalizeFilename
Gets the canonical file name from @filename. All triple slashes are turned into single slashes, and all .. and .s resolved against @relative_to.
Symlinks are not followed, and the returned path is guaranteed to be absolute.
If @filename is an absolute path, @relative_to is ignored. Otherwise,
Return
a newly allocated string with the canonical file path
Since
2.58
Parameters
filename
the name of the file
relativeTo
the relative directory, or null to use the current working directory