kunit: tool: add support for QEMU

Add basic support to run QEMU via kunit_tool. Add support for i386,
x86_64, arm, arm64, and a bunch more.

Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Tested-by: David Gow <davidgow@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>