-The `configure' script is built from `configure.ac' by the `autoconf'
-program. You need at least the version of autoconf specified in the
-AC_PREREQ(...) command to rebuild `configure' from `configure.ac'.
+The `configure' script is built from `configure.ac' by the
+`autogen.sh' script, which checks that `autoconf' and other build
+tools are sufficiently up to date and then runs the build tools.