[clang] [llvm] Enable ClangIR Build By Default (PR #221291)

[Erich Keane via cfe-commits]

erichkeane wrote:

> We're seeing errors failing to find include files: `fatal error: 'mlir/IR/BuiltinLocationAttributes.h.inc' file not found`. Is anyone else seeing the same thing? Any idea what could be causing it? https://github.com/qualcomm/cpullvm-toolchain/actions/runs/39650133307/job/119395984370

Yep!  We have a report of that here: https://github.com/llvm/llvm-project/issues/234321

A coworker put together a patch for this a while ago and forgot about it, but is actively working on getting it merged from here: https://github.com/llvm/llvm-project/pull/187692



https://github.com/llvm/llvm-project/pull/221291