There was a build architecture leaking into the target ptest which
could vary depending upon host. Remove it as its cosmetic.
[YOCTO #13770]
(From OE-Core rev: 37db519eedb7eb5cd4f14d05f30f5d580aa7458d)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>