tests: Fix "make check-functional" for targets without thorough tests

tests: Fix "make check-functional" for targets without thorough tests

If QEMU gets configured for a single target that does not have
any thorough functional tests, "make check-functional" currently
fails with the error message "No rule to make target 'check-func'".
This happens because "check-func" only gets defined for thorough
tests (quick ones get added to "check-func-quick" instead).
The same problem can happen with the quick tests for targets that
do not have any functional test at all. To fix it, simply make sure
that the targets are always available in the Makefile.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Closes: https://gitlab.com/qemu-project/qemu/-/issues/3119
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20250918125154.126072-1-thuth@redhat.com>