[clang] [llvm] [TargetParser][clang] Parse and store Intel IGCA virtual architecture as an OffloadArch (PR #227468)

[Ian Li via cfe-commits]

ianayl wrote:

> **1 previously missed issue**
These are currently TODO's: AMD carveout for IGCA potentially in another PR, and I need to think about if I want catch typos that "seem like IGCA", and what "it's a typo but the user probably meant IGCA" would even mean.

https://github.com/llvm/llvm-project/pull/227468