mktemp: make argument optional (coreutil 6.12 compat)

function                                             old     new   delta
mktemp_main                                          157     174     +17
packed_usage                                       24508   24504      -4
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(add/remove: 0/0 grow/shrink: 1/1 up/down: 17/-4)              Total: 13 bytes

2 files changed