OpenSSL supports out-of-tree builds so we should use them. This makes builds
more reliable, and makes it easier to reduce the size of the ptest package.
(From OE-Core rev: e028b4457781f60d8491a99a23011996fa913013)
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>