[llvm] workflows: Add missing apt-get update to abi tests (PR #133264)

[Tom Stellard via llvm-commits]

tstellar wrote:

> LGTM. Sorry for missing this. Transitive deps always seem to bite somewhere...

I don't think you broke this.  It stopped working in the release branch.

https://github.com/llvm/llvm-project/pull/133264