Build libclang_rt/profile on all clang-supported architectures

There's no reason why a special case needs to be added specifically for amd64,
arm, and i386, as the code is written in machine architecture agnostic C/C++.

This will make it possible for all supporting clang architectures to produce
runtime coverage with --coverage.

MFC after: 2 weeks
Reviewed by: dim
Differential Revision: https://reviews.freebsd.org/D20003