[llvm] [llvm-pdbutil] Avoid reading EC names from non-EC modules (PR #223253)

[Lakshay Chauhan via llvm-commits]

nos1dot618 wrote:

Could we add a regression test covering `llvm-pdbutil dump --modules` on a PDB containing a non-EC module, verifying that it succeeds?

https://github.com/llvm/llvm-project/pull/223253