emu: print when the first instruction commits

src/test/csrc/emu.cpp

@@ -274,6 +274,7 @@ uint64_t Emulator::execute(uint64_t max_cycle, uint64_t max_instr) {
       long get_img_size();
       ref_difftest_memcpy_from_dut(0x80000000, get_img_start(), get_img_size());
       ref_difftest_setregs(reg);
+      printf("The first instruction has commited. Difftest enabled. \n");
     }
 
     // difftest