autogen.sh overwriting INSTALL

[sgalgano]

Modifications introduced in ec89ef5 leads to INSTALL being overwritten when run.

[me@host emane]$ head INSTALL 
Build
=====

 # ./autogen.sh && ./configure && make

For information on configuration options see:

 # ./configure --help

Install
[me@host emane]$ ./autogen.sh -c
[me@host emane]$ ./autogen.sh
libtoolize: putting auxiliary files in '.'.
libtoolize: copying file './ltmain.sh'
libtoolize: putting macros in AC_CONFIG_MACRO_DIRS, 'm4'.
libtoolize: copying file 'm4/libtool.m4'
libtoolize: copying file 'm4/ltoptions.m4'
libtoolize: copying file 'm4/ltsugar.m4'
libtoolize: copying file 'm4/ltversion.m4'
libtoolize: copying file 'm4/lt~obsolete.m4'
configure.ac:53: installing './compile'
configure.ac:53: installing './config.guess'
configure.ac:53: installing './config.sub'
configure.ac:41: installing './install-sh'
configure.ac:41: installing './missing'
src/agents/gpsdlocation/Makefile.am: installing './depcomp'
[me@host emane]$ head INSTALL
Installation Instructions
*************************

Copyright (C) 1994-1996, 1999-2002, 2004-2013 Free Software Foundation,
Inc.

   Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.  This file is offered as-is,
without warranty of any kind.

[sgalgano]

Tested on F23 with autoreconf 2.69.