Enable simulator on gdb

[任建军]

Hi all:
   I have a complie question, An help me answer it? 
   I use binutils-gdb source code to build gdb for aarch64，the version is “gdb-9.2-release”,   and complie command line is "./configure --target=aarch64 --enable-sim".
   Compile is completed, but when i enter gdb and type command "target sim"  , gdb said  "Undefined target command: "sim": ..." ,  am i missed someting when i complie gdb? 


   And attach a picture:


   Thanks a lot！




 Best Regards！
 Ron