do not use syscall to quit emulation. this can fix issues #147 & #148

qemu/target-arm/translate-a64.c

@@ -10974,7 +10974,8 @@ static void disas_a64_insn(CPUARMState *env, DisasContext *s)
 
     // Unicorn: end address tells us to stop emulation
     if (s->pc == s->uc->addr_end) {
-        gen_exception_insn(s, 0, EXCP_SWI, 0);
+        // imitate WFI instruction to halt emulation
+        s->is_jmp = DISAS_WFI;
         return;
     }
 
@@ -11107,8 +11108,9 @@ void gen_intermediate_code_internal_a64(ARMCPU *cpu,
 
     // Unicorn: early check to see if the address of this block is the until address
     if (tb->pc == env->uc->addr_end) {
+        // imitate WFI instruction to halt emulation
         gen_tb_start(tcg_ctx);
-        gen_exception_insn(dc, 0, EXCP_SWI, 0);
+        dc->is_jmp = DISAS_WFI;
         goto done_generating;
     }