[clang] [Clang] Fixes builtin_bswapg builtin for bool type (PR #179177)

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woruyu wrote:

> Sorry, have been swamped with Actual Job(tm) stuff, I'd like to reiterate @shafik's comments - can we have a follow up PR for the negative cases (unsupported bitwidths and the like)

It's easy to refactor to a meaning function name. But I don't know whether we need to deal with bit widths between 2 and 7. Friendly ping @RKSimon , @tbaederr 

https://github.com/llvm/llvm-project/pull/179177