[clang] [CIR] Add math and builtin intrinsics support (PR #175233)

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adams381 wrote:

@andykaylor Apologies for missing those comments. I've addressed the fall-through issue in commit b2acad44fee5 - added `errorNYI` after `BI_setjmp` to prevent the setjmp/exception builtins from incorrectly falling through to the `BImove`/`BIforward` handler.

https://github.com/llvm/llvm-project/pull/175233