The version you requested (5.6.30+dfsg-0+deb8u1) is not available, but a newer one is (5.6.33+dfsg-0+deb8u1). We redirected you there.
This file is indexed.

/usr/lib/php5/build/config.sub is in php5-dev 5.6.33+dfsg-0+deb8u1.

This file is owned by root:root, with mode 0o777.

It is a symlink to /usr/lib/php5/build/../../../share/misc/config.sub