[llvm] [VP] Refactor VectorBuilder to avoid layering violation. NFC (PR #99276)

[Fraser Cormack via llvm-commits]

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@@ -599,6 +599,19 @@ Intrinsic::ID VPIntrinsic::getForOpcode(unsigned IROPC) {
   return Intrinsic::not_intrinsic;
 }
 
+Intrinsic::ID VPIntrinsic::getForIntrinsic(Intrinsic::ID Id) {
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frasercrmck wrote:

Could this be made `constexpr`? I see you're using it with a constant `RecurKind::FAdd` later on.

https://github.com/llvm/llvm-project/pull/99276