CI: Revise builds with older autoconf and related tool kits

[jimklimov]

This should address issue #1168 (some fallout after PRs #1151 and #1159) - at least this passed on a test system with Ubuntu 14.04 that failed to build before the PRed change.

[jimklimov]

Now this PR also rearranged the ci_build.sh script to not generally start (loops) with a distcheck, destined to spend a minute re-configuring to update a Makefile to delete it, and then configure again for the build.

[jimklimov]

Also discovered a bit of heads-up for people like me, who develop or debug shell scripts in the product or ecosystem nearby: I recently found that the expr shell utility/builtin is geared towards boolean evaluations, so any expressions that return a numeric zero mean a "false" exit-code.

For example, expr 1 - 1 or expr -2 + 2 would fail (return exit-code 1) while expr 2 - 1 and other non-zero maths would not (they return exit-code 0) .

Since many of our infra and maybe prod scripts do portable maths with expr (so they don't rely on particular shell's abilities like bash's N=$(($N-1)) or availability of third-party tools like bc), without realizing such edge case before, this is a "strange failure" mode to be on lookout for when something "crazy" happens.

Safety fencing with || true or checking in case of error that the returned string is "0" (and not some other error) may be due.