tst-setuid1-static-ENV: Add $(common-objpfx)nss [BZ #26820]

commit def67465
Author: Florian Weimer <fweimer@redhat.com>
Date:   Mon Apr 27 15:00:14 2020 +0200

    nptl/tst-setuid1-static: Improve isolation from system objects

    Static dlopen needs an LD_LIBRARY_PATH setting to avoid loading system
    libraries.

missed $(common-objpfx)nss.  Add $(common-objpfx)nss to LD_LIBRARY_PATH
for tst-setuid1-static to support

  struct passwd *pwd = getpwnam ("nobody");

in nptl/tst-setuid1.c.