Usee POSIX atomic file install instead of copying from TMPDIR

[diekhans]

LyRic would be faster and more robust if it used POSIX atomic file creation instead of writing to TMPDIR and then
copying in place.

TMPDIR is usually on a separate file system, so

mv {TMPDIR}/$uuidTmpOut {output.bam}

Would usually be a copy. If there is an error, such as out of disk space, an incomplete output file
out exist.

If the file is created on the same file system as the output file, so the mv is an atomic rename.
In bash I would do:

tmpout=${outbam}.tmp
do_something  > ${tmpout}
mv -f ${tmpout} ${outbam}

Assuming bash is run with -e, the completed file doesn't exist under
the final name until it is successfully completed, and there is no copy overhead.