x86emul: suppress "not built" warning for test harness'es run targets

x86emul: suppress "not built" warning for test harness'es run targets

The run* targets can be used to test whatever the tool chain is capable
of building, as long as at least the main harness source file builds.
Don't probe the tools chain, in particular to avoid issuing the warning,
in this case. While looking into this I also noticed the wording of the
respective comment isn't quite right, which therefore gets altered at
the same time.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>