Question about dub and imports

[Jonathan Villa via Digitalmars-d-learn]

I'm trying to build a vibe.d application, but I made a little 
library (just source code) that I want to add to the project.

So, in the generated dub.sdl file I added at the end:
sourcePaths "../D/src"
sourceFiles "../D/src/alfred/package.d"

The problem is at build time DUB tries to create a library file 
and it fails.
I don't want to it to create a .lib file, just "look at this path 
so when I write `import alfred;` you know where this refers to`.

I'm pretty new using the dub thing, I have look in 
https://code.dlang.org/package-format?lang=sdl but I get a little 
confused.

I have already did this in a non-dub project, adding the import 
path with -I and listing the files and it never actually 
generated a lib.

Or is there a way to just inject a direct line to the build 
params like "-I../D/src" alfred/types.d alfred/command.d ...(etc) 
when running dub in my vibe-d project???

(Is really neccesary to look my little source library like a .lib 
file and try to generate it?)

JV