[bcl] Look in all .sources files when gathering files to dist

[bcl] Look in all .sources files when gathering files to dist

Previously we would only look into files ending in libraryname.sources.
This breaks down in cases where we used e.g. "#include common.sources"
because those files don't match the pattern and would be left out.

To fix this we could either start resolving includes in the .sources,
but the simpler fix is to just dist files from all normal .sources files.