[llvm] [X86] With large code model, put functions into .ltext with large section flag (PR #73037)

[Fangrui Song via llvm-commits]

MaskRay wrote:

On the linker side (I am mostly nervous about), you can use a linker script fragment for the experiment  https://sourceware.org/binutils/docs/ld/Miscellaneous-Commands.html#index-INSERT

On the compiler side, I think we may need something like this. Some JIT large code model users may hard code the `.text` section name and the change could cause them a trouble, so an opt-out option may be needed.

https://github.com/llvm/llvm-project/pull/73037