[clang] [Serialization] Don't write merged table (PR #186056)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

> > could you test this with your internal workloads for correctness and compilation time performance.
> 
> The failing modules test isn't a correctness concern?

If you're talking about the above test, yes, it is not a correctness concern. On the one hand, it is test for C++20 modules for recompilability. On the other hand, it simply makes the test result better as it avoid unnecessary changes.  You can look into https://clang.llvm.org/docs/StandardCPlusPlusModules.html#experimental-non-cascading-changes if you're interested

https://github.com/llvm/llvm-project/pull/186056