Bug#924140: README: please mention STRICT_ERROR_CHECKS=1 USE_SAMPLE_FILES=1

Package: www.debian.org
Severity: normal
User: [email protected]
Usertags: scripts

Hi,

While working on rebuilding the website within stretch and buster, I've
noticed the following.

It was a bit surprising to see that many errors, either due to missing
dependencies, or missing data, were not leading to a global failure when
the top-level make returns.

It was also a bit surprising to see that some targets couldn't get
processed successfully.

It turned out that the former issue is at least partiallly fixed by
setting STRICT_ERROR_CHECKS=1; the latter can be worked around by
setting USE_SAMPLE_FILES=1, which sets up some sample data files for
files that would otherwise be set up by some sync scripts getting run
from cron. Examples include:

    $(ENGLISHSRCDIR)/devel/people.names
    $(DATADIR)/Maintainers
    $(ENGLISHSRCDIR)/$(CUR_DIR)/data/%
    $(L10N_DIR)/data/%
    $(ENGLISHDIR)/mirror/Mirrors.masterlist

That was implemented in:
  https://salsa.debian.org/webmaster-team/webwml/commit/f0290accd46ee45383b56b9acc9624f5707f6b0e

(Thanks, Wouter!)

It seems to me it would make sense to mention both variables in the
top-level README, so that people interested in working on a full build
wouldn't have to figure out why some targets seem to be missing or not
defined, and to track down individual READMEs like:

     english/mirror/Mirrors.masterlist.README

FWIW, that's also what's getting used for CI, see:

    README_CI.gitlab-ci.yml


Cheers,