Hi everyone, At present, there are many LLVM related codes in code base, but these codes are not really used. During my attempt to upgrade GCC, I found that the higher version of GCC is not compatible with the LLVM 3.4.2 version currently used by Doris. I propose to delete all LLVM related code in the code. With this deletion, we can gain the following benefits
1. Remove irrelevant code to make our code more refined 2. Ability to upgrade our toolchain from GCC7 to GCC9 or higher 3. In the future we will be able to use later versions of LLVM. The APIs of the LLVM versions are not compatible, and there is no way to smoothly upgrade to a higher version. And a large amount of code that is no longer used will become a constraint on our future use of higher versions of LLVM. Since our LLVM code is not really used, this operation will not bring other harm. Looking forward to your feedback, if there is no objection, I will gradually complete this operation later. Thanks, Zhao Chun
