Remove SetObjectModificationTime which is not currently used, and assigns to the wrong member.
Sometimes these odd leaf APIs are used by custom downstream variants of LLDB, but without any comment pointing into that direction and no unit test, I think this makes sense to remove. Also, we can easily add it back in later.
The largest downstream LLDB fork that I know about is swift-lldb, which is also open source and thus easy to check. There also exists a Rust version, and many custom forks for various specialized hardware. Putting patches up for review here gives the maintainers a chance to voice their concerns. For larger architectural changes we usually have a thread on lldb-dev to make sure we captured everyone's attention. We're under no obligation to not break anyone's private fork, but if there is an easy/reasonable way to make everyone happy we usually tend to choose that path.
I should also mention that we are actively looking into ways to upstream the swift-lldb code into llvm.org. Now that both branches are licensed under Apache the only challenge left is to make the Swift support a real language *plugin* that can be conditionally compiled.