enable fuzzing trusty targets automatically

The non-test fuzz targets should run automatically in Haiku.

None of these should be built for Host, and all but the
trusty_test_fuzzer should be built for Target.

Test: built locally (make haiku) and checked that non-test trusty fuzz
targets are included as expected.

Change-Id: Ic67b1e1ddea8ed61b83deef66acdeb0891489195