[clang] [clang][ssaf] Fix nondeterministic test failures of clang/test/Analysis/Scalable/call-graph.cpp (PR #190155)

[Balázs Benics via cfe-commits]

steakhal wrote:

It seems some linux jobs have already passed check-clang, so this should be safe to land. I postpone this fix any longer.
I'll fix the raised comments in followups if necessary.

https://github.com/llvm/llvm-project/pull/190155