[llvm] [VPlan] Implement VPWidenCallRecipe::computeCost (NFCI). (PR #106047)

[David Spickett via llvm-commits]

DavidSpickett wrote:

This is also the cause of test suite failures on AArch64 Linux: https://lab.llvm.org/buildbot/#/builders/41/builds/1722

It's just that build configuration issues are hiding them under a pile of unintentional NOEXE results. We'll find what is actually failing.

https://github.com/llvm/llvm-project/pull/106047