[nmh-workers] Reproducible build patch

[Ken Hornstein]

We received the following bug report today:

        http://savannah.nongnu.org/support/?109535

It seems to me like reproducible builds are probably a pretty good idea
and nmh should support them, and the patch looks relatively small.  But
to be completely portable the date line should be (from here):

https://wiki.debian.org/ReproducibleBuilds/TimestampsProposal#Bash_.2F_POSIX_shell

DATE_FMT="%Y-%m-%d %T +0000"
SOURCE_DATE_EPOCH="${SOURCE_DATE_EPOCH:-$(date +s)}"
date=$(TZ=GMT0 date --date="@$SOURCE_DATE_EPOCH" "+$DATE_FMT" 2>/dev/null || 
date -u -r "$SOURCE_DATE_EPOCH" "+$DATE_FMT" 2>/dev/null || date -u 
"+$DATE_FMT")

I ... think that's right (note, I haven't tested it yet).  Everyone ok
with this?

--Ken