syscall: Readlink is incorrect for windows

[gooid]

`

------------------------ src/syscall/syscall_windows.go ------------------------
index 703bb53..eb9a7e1 100644
@@ -1028,11 +1028,11 @@ func Readlink(path string, buf []byte) (n int, err error) {
case IO_REPARSE_TAG_SYMLINK:
data := (symbolicLinkReparseBuffer)(unsafe.Pointer(&rdb.reparseBuffer))
p := ([0xffff]uint16)(unsafe.Pointer(&data.PathBuffer[0]))

•   s = UTF16ToString(p[data.PrintNameOffset/2 : (data.PrintNameLength-data.PrintNameOffset)/2])
  

•   s = UTF16ToString(p[data.PrintNameOffset/2 : (data.PrintNameLength+data.PrintNameOffset)/2])
  

  case _IO_REPARSE_TAG_MOUNT_POINT:
  data := (mountPointReparseBuffer)(unsafe.Pointer(&rdb.reparseBuffer))
  p := ([0xffff]uint16)(unsafe.Pointer(&data.PathBuffer[0]))

•   s = UTF16ToString(p[data.PrintNameOffset/2 : (data.PrintNameLength-data.PrintNameOffset)/2])
  

•   s = UTF16ToString(p[data.SubstituteNameOffset/2 + 4 : (data.SubstituteNameLength+data.SubstituteNameOffset)/2])
  

  default:
  // the path is not a symlink or junction but another type of reparse
  // point

`

[bradfitz]

/cc @alexbrainman

[hirochachacha]

Dup of #15978.

[alexbrainman]

Yes, looks like related to issue #15978.

Alex