xbps_set_cb_xxx: simplify by using vars on the stack.
xbps_set_cb_xxx: simplify by using vars on the stack.

stpx/xbps,datenwolf/xbps,stpx/xbps,datenwolf/xbps,ebfe/xbps,stpx/xbps,datenwolf/xbps,ebfe/xbps,ebfe/xbps