[llvm] [MC] Explicitly request executable stacks (PR #93478)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> Thanks @MaskRay .
> 
> @vzakhari @kiranchandramohan would it make sense to allocate the trampoline buffer somewhere else other than the stack? Say, on the heap and free it upon leaving the function (it needs to be allocated just once per function as it is conceptually a temporary of the argument evaluation, so in that sense it is a bit like an `allocatable`).
> 
> We could use the Fortran runtime to allocate an executable buffer.

Thanks. I'll request changes as I believe we don't want to support executable stacks or make easy for people to use it.

https://github.com/llvm/llvm-project/pull/93478