timeless build

[milahu]

add option for "timeless build" = on build, dont update these times:

site/index.xml
<lastBuildDate>Wed, 08 Jun 2022 08:57:59 +0000</lastBuildDate>

site/index.atom
<updated>2022-06-08T08:57:59.732044+00:00</updated>

these updates produce "diff noise" when the build is stored in git

workaround: remove the tags from site/index.xml and site/index.atom

sed -i -E 's|<lastBuildDate>[^<]+</lastBuildDate>||g' site/index.xml
sed -i -E 's|<updated>[^<]+</updated>||g' site/index.atom

[l29ah]

Also, the use of updated in tg-archive seems to violate the atom RFC:

4.2.15.  The "atom:updated" Element

   The "atom:updated" element is a Date construct indicating the most
   recent instant in time when an entry or feed was modified in a way
   the publisher considers significant.

while tg-archive just puts the current time in, it seems.