/usr/src/glibc/debian/debhelper.in/libnss-files-udeb.install is in eglibc-source 2.19-0ubuntu6.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | # FIXME: someday we may need to handle installing into non-lib.
TMPDIR/SLIBDIR/libnss_files*.so* lib
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