Properly handle extra "clean" targets with coq_makefile.
Properly handle extra "clean" targets with coq_makefile.

letouzey/coq-wip,ejgallego/coq,Lionel-Rieg/coq,Ptival/coq,ejgallego/coq,coq/coq,mlasson/coq,ejgallego/coq,SkySkimmer/coq,Zimmi48/coq,asr/coq,8l/coq,barras/coq,william-lawvere/coq,TOSPIO/coq,letouzey/coq-wip,silene/coq,ppedrot/coq,JasonGross/coq,maximedenes/coq,TOSPIO/coq,TheTypoMaster/coq,gares/coq,mlasson/coq,Zimmi48/coq,coq/coq,gares/coq,ppedrot/coq,Zimmi48/coq,aspiwack/coq,SkySkimmer/coq,ale-f/coq,ale-f/coq,letouzey/coq-wip,Zimmi48/coq,maximedenes/coq,JasonGross/coq,gares/coq,Matafou/coq,barras/coq,gmalecha/coq,TheTypoMaster/coq,Lionel-Rieg/coq,asr/coq,maximedenes/coq,herbelin/github-coq,gares/coq,ppedrot/coq,aspiwack/coq,Ptival/coq,Matafou/coq,TheTypoMaster/coq,amintimany/coq,asr/coq,JasonGross/coq,gmalecha/coq,mattam82/coq,mattam82/coq,Matafou/coq,maximedenes/coq,SkySkimmer/coq,Lionel-Rieg/coq,ale-f/coq,letouzey/coq-wip,jpdeplaix/coq,gares/coq,amintimany/coq,barras/coq,silene/coq,ppedrot/coq,Ptival/coq,william-lawvere/coq,coq/coq,letouzey/coq-wip,SkySkimmer/coq,william-lawvere/coq,amintimany/coq,mattam82/coq,jpdeplaix/coq,gmalecha/coq,aspiwack/coq,8l/coq,maximedenes/coq,silene/coq,herbelin/github-coq,8l/coq,ejgallego/coq,JasonGross/coq,mlasson/coq,herbelin/github-coq,TOSPIO/coq,jpdeplaix/coq,coq/coq,ppedrot/coq