Clarify bugpoint documentation regarding output
Clarify bugpoint documentation regarding output

Bugpoint's current documentation does specify that the result of a run is stored as the current design,
however it's easy to skim over what that means in practice. 

Add a documentation comment to explain specifically that an after bugpoint `write_xyz` pass is required to save
the reduced design.
cliffordwolf/yosys,cliffordwolf/yosys,YosysHQ/yosys,YosysHQ/yosys,YosysHQ/yosys,cliffordwolf/yosys,YosysHQ/yosys,YosysHQ/yosys,antmicro/yosys,antmicro/yosys,cliffordwolf/yosys,cliffordwolf/yosys,YosysHQ/yosys,cliffordwolf/yosys,antmicro/yosys,cliffordwolf/yosys,antmicro/yosys,cliffordwolf/yosys,YosysHQ/yosys,cliffordwolf/yosys,antmicro/yosys,YosysHQ/yosys,antmicro/yosys,antmicro/yosys,antmicro/yosys