busybox

ash: use F_DUPFD_CLOEXEC and O_CLOEXEC

function                                             old     new   delta
setjobctl                                            371     367      -4
setinputfile                                         226     220      -6
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(add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-10)             Total: -10 bytes

Based on patch by Mark Marshall <mark.marshall@omicronenergy.com>

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>