Testing with --target=FOO

[Ben Elliston]

When --target= is specified to sid's configure script, the sid
Makefiles build generic components and components related to that
target.  For example, the ARM reference timer is only built when all
targets are enabled or if --target=arm-*.

This causes problems when testing builds with --target specified.
Many of the generic components require a CPU component as part of the
simulation to be tested.  Frequently, we have used the more-dependable
hw-cpu-arm7t.

When the build is configured for other specific targets, the
hw-cpu-arm7t is not built and huge portions of the testsuite fails.
I'd like to discuss solutions to this problem.

Ideas I have had thus far (in increasing order of preference):

 + Mark such tests as "untested".

 + Build a small dummy CPU component that can be compiled
   unconditionally.  This will take time to write and may not be
   adequate for the kinds of tests we need to do.

 + Build the arm7t model unconditionally, regardless of the target.
   Only the cpu is required as far as I can tell.

Thoughts?

Ben