libtool 已安装但 buildconf 未找到

我正在尝试为 ARM 交叉编译 Apache httpd。这是我所做的：

$ sudo apt install libtool
$ git clone https://github.com/apache/httpd.git
$ cd httpd
$ svn co http://svn.apache.org/repos/asf/apr/apr/trunk srclib/apr
$ ./buildconf

输出是：

found apr source: srclib/apr
rebuilding srclib/apr/configure
buildconf: checking installation...
buildconf: python version 3.5.6 (ok)
buildconf: autoconf version 2.69 (ok)
buildconf: libtool not found.
           You need libtool version 1.4 or newer installed
           to build APR from SVN.
./buildconf failed for apr

但libtool已安装：

$ sudo apt install libtool
Reading package lists... Done
Building dependency tree       
Reading state information... Done
libtool is already the newest version (2.4.6-0.1).