Disable DTRACE on powerpc64-CURRENT. It is known not to link on elfv2.

Rather than conditionalize the inclusion on elfv2, I am asssuming the
userbase of erlang on powerpc64-CURRENT is still tiny. Effort would
better be spent on investigating the general problem on powerpc64.

PR: 240458 240461 240501 240502
Submitted by: pkubaj
Approved by: erlang (maintainer-timeout, > 2 weeks)