[llvm] [CGSCC] Fix compile time blowup with large RefSCCs (PR #94815)

[via llvm-commits]

SvyatoslavScherbina wrote:

Hi folks! Thank you, @aeubanks, for this improvement that fixed one of the blockers ([KT-68417](https://youtrack.jetbrains.com/issue/KT-68417)) for updating LLVM in Kotlin ([KT-49279](https://youtrack.jetbrains.com/issue/KT-49279)).
Thanks to @alinas as well, of course.


https://github.com/llvm/llvm-project/pull/94815