cxxrtl: treat assignable internal wires used only for debug as locals.
cxxrtl: treat assignable internal wires used only for debug as locals.

This issue was introduced in commit 4aa65f40 while fixing #2739.

Fixes #2882.

cliffordwolf/yosys,antmicro/yosys,YosysHQ/yosys,cliffordwolf/yosys,YosysHQ/yosys,YosysHQ/yosys,cliffordwolf/yosys,cliffordwolf/yosys,antmicro/yosys,antmicro/yosys,cliffordwolf/yosys,YosysHQ/yosys,YosysHQ/yosys,cliffordwolf/yosys,cliffordwolf/yosys,antmicro/yosys,YosysHQ/yosys,antmicro/yosys,antmicro/yosys,cliffordwolf/yosys,YosysHQ/yosys,antmicro/yosys,antmicro/yosys,cliffordwolf/yosys,YosysHQ/yosys