automake 1.15 requirement

Hello,

I notice the following behavior and would like to check if it is expected.
- If I bootstrap, configure and make on a CentOS 7 system with
automake 1.13, all looks fine.
- If I bootstrap, configure and make on a modern system with automake
1.15, all looks fine.
- but, if I bootstrap on a modern system with automake 1.15, move the
files to a CentOS 7 system with automake 1.13, then configure and
make, the make step fails immediately as follows:

$ make
CDPATH="${ZSH_VERSION+.}:" && cd . && /bin/sh
/repo/tdescham/ctng/crosstool-ng/scripts/missing aclocal-1.15
/repo/tdescham/ctng/crosstool-ng/scripts/missing: line 81:
aclocal-1.15: command not found
WARNING: 'aclocal-1.15' is missing on your system.
         You should only need it if you modified 'acinclude.m4' or
         'configure.ac' or m4 files included by 'configure.ac'.
         The 'aclocal' program is part of the GNU Automake package:
         <http://www.gnu.org/software/automake>
         It also requires GNU Autoconf, GNU m4 and Perl in order to run:
         <http://www.gnu.org/software/autoconf>
         <http://www.gnu.org/software/m4/>
         <http://www.perl.org/>
make: *** [aclocal.m4] Error 127

To be exact, I use the maintainer/create-release.sh script to get a
tarball of crosstool-ng that can then be deployed on different
machines. This means that in order to support CentOS 7 for
crosstool-ng, releases should be created from a similar system, and
not from a more modern system with automake 1.15.

Is this behavior expected? Or is there a solution so that even if
bootstrap happens with automake 1.15, usage with automake 1.13 will
still work?

Thanks,
Thomas