Fix build welding rigs with charged makeshift welder and welder.

Fixes #9420

It seems that bug was caused by not checking the availability of the tool before checking for enough of tool and components. That way it would always check for 2 welders (one as tool and one as components) and always check for 3 makeshift welders. Now it only checks for 2 welders if the character has a welder with enough charges (`tq->available == a_true`, so the tool requirement is fulfilled).