Hi, automake-1.15 behaves differently when AC_CONFIG_AUX_DIR is specified
after AC_USE_SYSTEM_EXTENSIONS (example attached which worked with
automake-1.14.1):

  $ autoreconf -vfi
  $ ./configure
  configure: error: cannot find install-sh, install.sh, or shtool in "." "./.." "./../.."

I think this is result of the commit:
http://git.savannah.gnu.org/cgit/automake.git/commit/?h=minor&id=7bc592708cc65

I believe that it is bad practice (and probably not-a-bug itself) and
AC_CONFIG_AUX_DIR should be specified as soon as possible, but we do not
have this documented (yet).  Thats why I write to bug-automake.  Maybe we
could install some AC_BEFORE warnings into autoconf but I would like to
discuss it here.
And at least it is good to have documented that behavior changed upstream.

Original bugreport: 
https://bugzilla.redhat.com/show_bug.cgi?id=1179182

Pavel