libbb: fix bb_strtol[l]'s check for "-". Hopefully closes bug 4174

function                                             old     new   delta
bb_strtol                                             82      85      +3
handle_errors                                         75      66      -9
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(add/remove: 0/0 grow/shrink: 1/1 up/down: 3/-9)               Total: -6 bytes

1 file changed