[clang] [ASTWriter] Do not write ObjCCategories if empty. (PR #141841)

[David Green via cfe-commits]

davemgreen wrote:

> This change makes sense to me. I have two questions:
> 
> 1. Can we add a test that checks that the block is omitted? (maybe via `llvm-bcanalyzer -dump`)
> 2. Can we make the `explicit-build.cpp` test more robust? (possibly by writing out import signatures)

Thanks - For 1 I can do. I'll see about adding a test.

For 2 I'm not sure. I was thinking of adding a triple to make sure it more reliable and less likely to go wrong on different architectures, but excluding the objc info was enough to get it working again for me. As for adding a import signature I'm not an expert, it certainly sounds sensible to have something more precise than the timestamp if what the test is testing is an important thing to get right.

https://github.com/llvm/llvm-project/pull/141841