[clang] [lld] [llvm] [mlir] [NFC][IWYU] Update Support library with IWYU. (PR #102707)

[Jay Foad via cfe-commits]

jayfoad wrote:

> > Did you know that LLVM intentionally does not follow IWYU and favors forward declarations: https://llvm.org/docs/CodingStandards.html#include-as-little-as-possible
> 
> Yes, but I actually do not see what part of the mentioned standard' section conflicts with the change.

Could you try preprocessing each affected source file (i.e. compile it with -E) and see whether the total number of included source lines goes up or down? I think that would help to demonstrate whether this patch violates the "include as little as possible" philosophy.

https://github.com/llvm/llvm-project/pull/102707