/usr/lib/php5/build/libtool.m4 is in php5-dev 5.4.45-0+deb7u2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/php5/build/../../../share/aclocal/libtool.m4
/usr/lib/php5/build/../../../share/aclocal/libtool.m4