[clang] Control spacing for attribute printing (PR #174197)

[Kim Gräsman via cfe-commits]

kimgr wrote:

@vgvassilev @erichkeane You worked on this in https://github.com/llvm/llvm-project/pull/88600 -- let me know what you think.

We still post-process printed decls to produce forward-declarations in IWYU, and this would help eliminate some noise.

I don't have merge permissions, and so would need a hand with merging if this makes sense.

https://github.com/llvm/llvm-project/pull/174197