[llvm] [polly] [Support] Remove llvm/Support/Host.h (PR #74261)

[Sam Elliott via llvm-commits]

lenary wrote:

This didn't happen before because it is used by vebdored isl code in Polly, as this diff shows. I'm not sure the status of updating that code, but the (external) author was informed a while ago about needing to update. I don't know who maintains Polly and whether they accept direct changes to vendored code or whether changes have to go upstream first.  

https://github.com/llvm/llvm-project/pull/74261