bug#27736: OSX 10.6.8: Building from master branch fails.

[Charles A. Roelli]

No worries.  The fix is pushed to emacs-26, and it should make it over
to the master branch soon.

  commit 98288ecaffbc0947ec3193088172ea85ad5e42a5
  Author: Charles A. Roelli <charles@aurox.ch>
  Ref:    emacs-26
  Date:   Wed Nov 8 20:51:48 2017 +0100

  Further workaround for faulty localtime() under macOS 10.6

  * lisp/org/org-clock.el (org-clock--oldest-date): Fix an issue
  when compiling on macOS 10.6 with a western time zone (a
  continuation of Bug#27736).  In particular, see:

  https://debbugs.gnu.org/cgi/bugreport.cgi?bug=27736#74

  and the first commit that attempted to work around this problem,
  "Workaround for faulty localtime() under macOS 10.6", bd49b6f1 of
  2017-09-30.