[cs] don't try to clean output directory when -D unity-std-target for now
[cs] don't try to clean output directory when -D unity-std-target for now

pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe