При сборке pecl расширения в gentoo может возникнуть ошибка:
libtool: Version mismatch error. This is libtool 2.4.2, but the
libtool: definition of this LT_INIT comes from an older release.
libtool: You should recreate aclocal.m4 with macros from libtool 2.4.2
libtool: and run autoconf again.
Решается так:
$ phpize
$ aclocal && libtoolize --force && autoreconf
$ ./configure bbbb#again