basedir for rebased url duplicated

[ray007]

I'm trying to concat 4 css files which have in total 4 url() directives, one of which is a data-url.
Two others point to an image in folder img and are fine, the last one is material icons in folder lib/m.
Unfortunately the attempted font-load has become

url("lib/lib/m/MaterialIcons-Regular.ttf")

Note: interestingly enough, moving the call to concatCSS to before cleanCSS seems to make things work.
But the @font-face for material icons is missing completely in this case, not sure how font family "Material Icons" is resolved on my machine in this case.