configure script does not give error if "ar" is not found

[Gavin Smith]

Hello,

I was trying to build Texinfo on a SunOS 5.10 sparc system, but got an
error message when it tried to build gnulib, that "ar" didn't exist.
Looking at config.log I have:

configure:5731: checking for egrep
configure:5793: result: /usr/xpg4/bin/grep -E
configure:5800: checking for Minix Amsterdam compiler
configure:5824: result: no
configure:5876: checking for ar
configure:5906: result: no
configure:5983: checking for ranlib
configure:6013: result: no
configure:6037: checking for ANSI C header files


I found the following in gnulib-common.m4 that is probably responsible

  if test -z "$AR"; then
    if test $gl_cv_c_amsterdam_compiler = yes; then
      AR='cc -c.a'
      if test -z "$ARFLAGS"; then
        ARFLAGS='-o'
      fi
    else
      dnl Use the Automake-documented default values for AR and ARFLAGS,
      dnl but prefer ${host}-ar over ar (useful for cross-compiling).
      AC_CHECK_TOOL([AR], [ar], [ar])
      if test -z "$ARFLAGS"; then
        ARFLAGS='cru'
      fi
    fi
  else
    if test -z "$ARFLAGS"; then
      ARFLAGS='cru'
    fi
  fi

The problem is with the use of AC_CHECK_TOOL. The third argument given
is a default value, that doesn't exist. I suggest doing, instead
(untested):

AC_CHECK_TOOL([AR], [ar], []])
if test -z "$AR"; then
  AC_MSG_ERROR([ar program not found - cannot create static archives])
fi

(Please cc me on any responses)