The gl_PROG_AR_RANLIB (it is always called by gl_EARLY) sets AR
and ARFLAGS variables. Doing this unconditionally could break
later Automake's AM_PROG_AR invocation (at least it's
AC_CHECK_TOOLS call to detect correct 'ar' binary).
Original purpose of the gl_PROG_AR_RANLIB was only to handle the
Amsterdam Compiler Kit, so make the previous code to have effects
only on ACK, and rather automatically call the Automake's
AM_PROG_AR as soon as possible to decide other cases.
References:
http://lists.gnu.org/archive/html/bug-gnulib/2015-07/msg00001.html
* m4/gnulib-common.m4 (gl_PROG_AR_RANLIB): AC_BEFORE AM_PROG_AR.
Set the AR/ARFLAGS to ACK defaults OR call AM_PROG_AR. If neither
is possible, keep setting AR/ARFLAGS to reasonable defaults.
* gnulib-tool (func_import): Put the gl_USE_SYSTEM_EXTENSIONS
right before gl_PROG_AR_RANLIB into gnulib-comp.m4 (if the
'extensions' module is used.
* modules/extensions (configure.ac-early): Remove as this snippet
is added to gnulib-comp.m4 earlier anyway.
