protect qemu_cpu_kick_self for Win32

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/cpus.c b/cpus.c
index e0bcb5c..7559a02 100644
--- a/cpus.c
+++ b/cpus.c
@@ -867,12 +867,16 @@
 
 void qemu_cpu_kick_self(void)
 {
+#ifndef _WIN32
     assert(cpu_single_env);
 
     if (!cpu_single_env->thread_kicked) {
         qemu_thread_signal(cpu_single_env->thread, SIG_IPI);
         cpu_single_env->thread_kicked = true;
     }
+#else
+    abort();
+#endif
 }
 
 int qemu_cpu_is_self(void *_env)