/usr/share/postgresql/9.3/extension/postgis--2.1.0rc2--2.1.2.sql is in postgresql-9.3-postgis-scripts 2.1.2+dfsg-2.
This file is owned by root:root, with mode 0o644.
It is a symlink to /usr/share/postgresql/9.3/extension/./usr/share/postgresql/9.3/extension/postgis--2.1.2--2.1.2next.sql