tcmode-external-csl.inc: specify the path you couldn't find

tcmode-external-csl.inc: specify the path you couldn't find

While misconfiguring toolchains, I noticed that one of the
diagnostic messages gave me a little less information than I'd
like about what I'd done wrong.  Displaying the glob pattern
that couldn't be matched turns out to make it a lot easier to
figure out what you did wrong.  (Answer: Not enough coffee.)

(From OE-Core rev: 84d8b8846556cee191afb93016a2c38df8aaa7ba)

Signed-off-by: Peter Seebach <peter.seebach@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>