疑难杂症，高手搭救。请教configure 问题，configure.ac设置

事情是这样的。我现在需要编译一个程序包，但是直接./configure它显示permission denied。然后我看了下install，内容如下的default_fink_path=/PBC-0.4.7-vc-c 
，我的所有东西都在=/PBC-0.4.7-vc-c目录中：
This build system has been tested and works on Linux and Mac OS X with a
fink installation. You may need to specify paths via LDFLAGS and
CPPFLAGS if libraries are located in places other than the default
assumed in configure.ac. See ./configure --help for more information.

./configure
make
make install
************************************************************************
我按上面说的，把下面的configure.ac修改成
C/C++ code

#-*- Autoconf -*-
# Process this file with autoconf to produce a configure script.

AC_PREREQ(2.5)
AC_INIT([pbc], [0.4.7], [blynn@cs.stanford.edu])
AM_INIT_AUTOMAKE(pbc,0.4.7)
AM_CONFIG_HEADER(config.h)
AC_CONFIG_SRCDIR([./])
AC_PROG_LIBTOOL
#AC_CANONICAL_HOST

CFLAGS=
default_fink_path=/PBC-0.4.7-vc-c 
case $host_os in
     darwin*) 
               dnl nested function support
               AC_MSG_NOTICE([Adding -fnested-functions to CFLAGS])
          CFLAGS="-fnested-functions"

          dnl fink installation
               AC_MSG_CHECKING([for a fink installation at $default_fink_path])
               if test -d $default_fink_path; then 
               AC_MSG_RESULT([found it!])
         AC_MSG_NOTICE([Adding -I$default_fink_path/include to CPPFLAGS])
               CPPFLAGS="-I$default_fink_path/include $CPPFLAGS"
         AC_MSG_NOTICE([Adding -L$default_fink_path/lib to LDFLAGS])
         LDFLAGS="-L$default_fink_path/lib $LDFLAGS"
          else
        AC_MSG_RESULT(none)
        AC_MSG_NOTICE([You may need to add set CPPFLAGS and LDFLAGS for gmp, etc.])
          fi
          ;;
esac

# Checks for programs.
AC_PROG_CC
AC_PROG_CPP
AC_PROG_INSTALL
AC_PROG_LN_S
AC_PROG_MAKE_SET

# Checks for libraries.
lib_err_msg="add its path to LDFLAGS\nsee ./configure --help"
AC_CHECK_LIB( [m], [pow], [],[
          echo "************************"
          echo "m library not found"
          echo -e $lib_err_msg
          echo "************************"
          exit -1
          ])
AC_CHECK_LIB( [gmp], [__gmpz_init], [],[
          echo "************************"
          echo "gmp library not found"
          echo -e $lib_err_msg
          echo "************************"
          exit -1
          ])
dnl Reset libs because most programs do not need to link against all of these libs.
LIBS=

# Checks for header files.
AC_FUNC_ALLOCA
AC_HEADER_STDC
AC_CHECK_HEADERS([stdlib.h string.h sys/time.h])

# Checks for typedefs, structures, and compiler characteristics.
AC_C_CONST
AC_C_INLINE
AC_TYPE_SIZE_T
AC_HEADER_TIME

dnl setup CFLAGS
AC_ARG_ENABLE( optimized, 
           [AC_HELP_STRING([--enable-optimized],
            [Enable optimized build])],
         [with_enable_optimized="$withval"],
     [with_enable_optimized="no"])

CFLAGS="$CFLAGS -O2 -Wall -W -Wfloat-equal -Wpointer-arith -Wcast-align -Wstrict-prototypes -Wredundant-decls \
-Wendif-labels -Wshadow -pipe -ffast-math -U__STRICT_ANSI__ -std=c99"
if test "x$with_enable_optimized" != "no"; then
       CFLAGS="$CFLAGS -g"
else
    CFLAGS="$CFLAGS -fomit-frame-pointer -O3"
fi

# Checks for library functions.
AC_FUNC_MALLOC
AC_FUNC_REALLOC
AC_CHECK_FUNCS([floor gettimeofday memmove memset pow sqrt strchr strdup])

AC_CONFIG_FILES([Makefile example/Makefile gen/Makefile])
AC_OUTPUT

echo -ne "\n"
echo "global build variables"
echo "-----------------------------------------"
echo `date`
echo "host info:        $host"
echo "optimized build:  $with_enable_optimized"
echo "LDFLAGS:          $LDFLAGS"
echo "CPPFLAGS:         $CPPFLAGS"
echo "CFPLAGS:          $CFLAGS"
echo "-----------------------------------------"
echo -ne "\n"

然后，用./configure还是不行。但我还是不愿意这么早放弃，于是，
我按照生成configure文件的方式重新生成configure文件，但是中间出现了不少warning和一个error，后面的生成Makefile.am的过程也就无法继续了。我尝试继续到最后还是老样子不行。
该错误是在autoconf过程中说：可能没有定义AC_PROG_LIBTOOL！

请高手不吝赐教，小弟感激不尽。

你sudo ./configure呢