oss-fuzz: standardise on RPATH for the static-ish binaries

oss-fuzz: standardise on RPATH for the static-ish binaries

This includes a revert of commit e60df214998afc145ca482cab184691b3ddc3bb2.

We strictly require RPATH, not the modern RUNPATH for the behaviour
we need in oss-fuzz, which is that not just the first line of dependencies
but the full set of libraries used by the program are looked for in the
'$ORIGIN/lib' directory.

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Autobuild-User(master): Douglas Bagnall <dbagnall@samba.org>
Autobuild-Date(master): Thu Oct 22 14:10:04 UTC 2020 on sn-devel-184