SCons: Fix mono_root initialization
SCons: Fix mono_root initialization

As advised by @neikeq.

firefly2442/godot,NateWardawg/godot,vkbsb/godot,godotengine/godot,mcanders/godot,mcanders/godot,Faless/godot,firefly2442/godot,MarianoGnu/godot,josempans/godot,pkowal1982/godot,josempans/godot,godotengine/godot,NateWardawg/godot,ex/godot,vnen/godot,guilhermefelipecgs/godot,BastiaanOlij/godot,akien-mga/godot,akien-mga/godot,Zylann/godot,NateWardawg/godot,guilhermefelipecgs/godot,akien-mga/godot,sanikoyes/godot,godotengine/godot,godotengine/godot,Zylann/godot,groud/godot,sanikoyes/godot,ZuBsPaCe/godot,akien-mga/godot,firefly2442/godot,vkbsb/godot,NateWardawg/godot,pkowal1982/godot,guilhermefelipecgs/godot,ZuBsPaCe/godot,guilhermefelipecgs/godot,ex/godot,vkbsb/godot,mcanders/godot,ex/godot,Valentactive/godot,honix/godot,sanikoyes/godot,groud/godot,Valentactive/godot,ZuBsPaCe/godot,MarianoGnu/godot,BastiaanOlij/godot,ex/godot,ex/godot,okamstudio/godot,Zylann/godot,josempans/godot,Shockblast/godot,DmitriySalnikov/godot,okamstudio/godot,Faless/godot,Faless/godot,vnen/godot,DmitriySalnikov/godot,okamstudio/godot,MarianoGnu/godot,okamstudio/godot,Shockblast/godot,DmitriySalnikov/godot,Valentactive/godot,josempans/godot,vnen/godot,vkbsb/godot,pkowal1982/godot,okamstudio/godot,firefly2442/godot,ex/godot,MarianoGnu/godot,Shockblast/godot,honix/godot,Valentactive/godot,ex/godot,mcanders/godot,pkowal1982/godot,vnen/godot,Zylann/godot,sanikoyes/godot,vnen/godot,MarianoGnu/godot,josempans/godot,sanikoyes/godot,BastiaanOlij/godot,pkowal1982/godot,groud/godot,firefly2442/godot,pkowal1982/godot,akien-mga/godot,BastiaanOlij/godot,ZuBsPaCe/godot,ZuBsPaCe/godot,sanikoyes/godot,guilhermefelipecgs/godot,akien-mga/godot,Valentactive/godot,DmitriySalnikov/godot,BastiaanOlij/godot,godotengine/godot,Faless/godot,Shockblast/godot,vkbsb/godot,okamstudio/godot,ex/godot,Valentactive/godot,honix/godot,godotengine/godot,okamstudio/godot,Paulloz/godot,okamstudio/godot,Shockblast/godot,Zylann/godot,NateWardawg/godot,Zylann/godot,BastiaanOlij/godot,godotengine/godot,vnen/godot,ZuBsPaCe/godot,josempans/godot,ZuBsPaCe/godot,honix/godot,groud/godot,Faless/godot,Zylann/godot,BastiaanOlij/godot,guilhermefelipecgs/godot,vkbsb/godot,Paulloz/godot,okamstudio/godot,Paulloz/godot,josempans/godot,sanikoyes/godot,NateWardawg/godot,MarianoGnu/godot,groud/godot,firefly2442/godot,vkbsb/godot,NateWardawg/godot,vnen/godot,firefly2442/godot,vnen/godot,DmitriySalnikov/godot,NateWardawg/godot,josempans/godot,Paulloz/godot,groud/godot,pkowal1982/godot,BastiaanOlij/godot,akien-mga/godot,Faless/godot,guilhermefelipecgs/godot,MarianoGnu/godot,Faless/godot,akien-mga/godot,Paulloz/godot,Valentactive/godot,Valentactive/godot,mcanders/godot,NateWardawg/godot,Paulloz/godot,sanikoyes/godot,Paulloz/godot,honix/godot,firefly2442/godot,Faless/godot,DmitriySalnikov/godot,vkbsb/godot,godotengine/godot,ZuBsPaCe/godot,MarianoGnu/godot,mcanders/godot,Shockblast/godot,Shockblast/godot,honix/godot,DmitriySalnikov/godot,Zylann/godot,guilhermefelipecgs/godot,okamstudio/godot,Shockblast/godot,pkowal1982/godot