kunit: tool: Enable CONFIG_FORTIFY_SOURCE under UML

Since commit ba38961a069b ("um: Enable FORTIFY_SOURCE"), it's possible
to run the FORTIFY tests under UML. Enable CONFIG_FORTIFY_SOURCE when
running with --alltests to gain additional coverage, and by default under
UML.

Signed-off-by: Kees Cook <keescook@chromium.org>

kunit: tool: Enable virtio/PCI by default on UML

There are several tests which depend on PCI, and hence need a bunch of
extra options to run under UML. This makes it awkward to give
configuration instructions (whether in documentation, or as part of a
.kunitconfig file), as two separate, incompatible sets of config options
are required for UML and "most other architectures".

For non-UML architectures, it's possible to add default kconfig options
via the qemu_config python files, but there's no equivalent for UML. Add
a new tools/testing/kunit/configs/arch_uml.config file containing extra
kconfig options to use on UML.

Tested-by: José Expósito <jose.exposito89@gmail.com>
Reviewed-by: Daniel Latypov <dlatypov@google.com>
Signed-off-by: David Gow <davidgow@google.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Daniel Latypov <dlatypov@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>