[toplevel] Don't ignore output filename provided by user in -o
[toplevel] Don't ignore output filename provided by user in -o

This was a silly bug introduced in
675a1dc401eb9a5540ba5bc9a522c1f84d4c3d54 that forgot to properly
forward the command line option.

Thanks to @SkySkimmer for finding out the problem.

closes #7447

coq/coq,SkySkimmer/coq,silene/coq,gares/coq,maximedenes/coq,ppedrot/coq,ejgallego/coq,coq/coq,Zimmi48/coq,gares/coq,ppedrot/coq,ejgallego/coq,JasonGross/coq,coq/coq,maximedenes/coq,Matafou/coq,SkySkimmer/coq,ppedrot/coq,Zimmi48/coq,ejgallego/coq,Zimmi48/coq,silene/coq,ppedrot/coq,coq/coq,silene/coq,JasonGross/coq,gares/coq,Zimmi48/coq,ejgallego/coq,SkySkimmer/coq,maximedenes/coq,Matafou/coq,ppedrot/coq,maximedenes/coq,Matafou/coq,gares/coq,maximedenes/coq,JasonGross/coq,JasonGross/coq,gares/coq,SkySkimmer/coq