ltp: remove open-posix-testsuite build logs

We don't need to package the open-posix-testsuite build logs. Typically
these are just lines of "SUCCESS" but sometimes there will be compile
warnings, which will include build paths.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>