What determines RUNPATH in installed libs?

[Tim Rice]

If I configure samba-4.10.16 with these options,
	--libdir=/opt/lib/samba
	--with-modulesdir=/opt/lib/samba
	--with-privatelibdir=/opt/lib/samba/private
most libs will get installed with the correct RUNPATH but these
    bin/default/lib/util/libsamba-modules-samba4.inst.so
    bin/default/libcli/registry/libutil-reg-samba4.inst.so
    bin/default/libcli/util/python-ntstatus.inst.cpython-39.so
    bin/default/libcli/util/python-werror.inst.cpython-39.so
    bin/default/source3/libmessages-util-samba4.inst.so
    bin/default/source3/libsmbldap.inst.so
    bin/default/source4/lib/samba3/libsmbpasswdparser-samba4.inst.so
    bin/default/nsswitch/stress-nss-libwbclient.inst
    bin/default/source3/smbd/notifyd/notifyd-tests.inst
    bin/default/source3/versiontest.inst
will get installed with RUNPATH /opt/lib/samba and yet they all
need libs from /opt/lib/samba/private.

Are the dependencies listed somewhere in one of the files in the source tree?
Are they calculated at configure time?
Are they calculated at build time?
Any idea where I should look?

Thanks for your consideration.

-- 
Tim Rice				Multitalents
tim at multitalents.net