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

[Alexis Engelke via cfe-commits]

aengelke wrote:

Thanks for the dylib fix. But:

> > Currently this fails to link for the full build, and if you build just clang the binary is completely broken.
>
> Oh! Thank you for pointing that out! I am/was unaware of this.

I've pointed this out [several](https://discourse.llvm.org/t/rfc-enable-clangir-build-by-default/91730/22) [times](https://discourse.llvm.org/t/rfc-enable-clangir-build-by-default/91730/64) [on Discourse](https://discourse.llvm.org/t/rfc-enable-clangir-build-by-default/91730/87)...... I would've expected that at least the Clang/ClangIR maintainers do read these messages. :(

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