Created by: DannyIsFunny

【本PR工作】将develop分支合入的部分feature cherry-pick 到release/v2.6.0分支

• Python

  • modify functions of python opt (#3465 )
  • add --python_executable option for x86 compiling (#3443 )
  • bug fix, fix error in python lib compiling (#3470 )

• compiling Android&iOs

  • add build_android.sh and build_ios.sh (#3411 )

• BUG FIX

  • bug fix , fix the issue that paddle-lite can not compile on CentOs (#3469)
  • change https into http for third_party lib (#3467)

• x86

  • add API : GetMutableTensor and GetParamNames(#3099 )
  • add --shutdown_log method in x86 compiling (#3476 )
  • Fix x86 kernels in FeedGR project, add (#3478 )
  • add cxx_demo for Paddle-Lite x86 backend (#3482 )
  • update doc of Paddle-Lite x86 lib (#3509 )