If the lib dir is included in the sources of bsconfig.json, please make a warning.

[MiryangJung]

I put the lib dir in bsconfig.json and run build -w, and the build was run infinitely.

    "sources": [
      { "dir": "lib", "subdirs": true }
    ],

Of course, I found the cause of the problem by reading Doc, but I think it would be good to raise the warning.
It is expected that need to check lib is included in bsb_parse_sources.ml

2022-06-16.8.56.21.mov