The unwritten API contract expected of a VFS.getcwd() by mp_vfs_getcwd()
is that its return value should be either "" or "/" when the CWD is at
the root of the VFS and otherwise start with a slash and not end with a
slash. This was not correctly implemented in VfsPosix for instances with
a non-empty root - the required leading slash, if any, was cut off
because the root length includes a trailing slash. This would result in
missing slashes in the middle of the return value of os.getcwd() or in
uninitialized garbage from beyond a string's null terminator when the
CWD was at the VFS root.
Signed-off-by: Christian Walther <cwalther@gmx.ch>
