This allows the use of native signalfd instead of the sigtimedwait
based emulation on systems other than Linux.

Signed-off-by: Kacper Słomiński <kacper.slominski72@gmail.com>
Message-Id: <20210905011621.200785-1-kacper.slominski72@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>