bug: `dotnet fsharplint lint existingFile1.fs existingFile2.fs` only analyzes the last file

[knocte]

Steps to reproduce: dotnet fsharplint lint existingFile1.fs existingFile2.fs
Current results:

========== Linting existingFile2.fs ==========
========== Finished: 0 warnings ==========
========== Summary: 0 warnings ==========

Expected results:
Either analyze all (both) files, or give error saying that only one file is supported at a time.