pth is not portable to uclibc therefore we need to exclude it for
uclibc based systems.
(From OE-Core rev: 6482f276533f3a177e07def9d616958d9bbc10c6)
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>