[P0] Update the llvm release

[ShangkunLi]

Due to some bugs/warnings emerging under the current LLVM release, we need to update the LLVM release to the latest llvm 20.1.7 https://github.com/llvm/llvm-project/tree/llvmorg-20.1.7.

The commit id is 6146a88.

[ShangkunLi]

Solved in #46

[yuqisun]

Got it, will update #19 accordingly.