vndk-def: Fix unittests with rpath

This commit adds -Wl,--disable-new-dtags to the unit tests that expect
DT_RPATH entries.  The latest toolchain defaults to --enable-new-dtags
now, thus we have to specify -Wl,--disable-new-dtags explicitly.

Bug: 64503245
Test: ./tests/test_elfdump.py

Change-Id: Idc78f183d3ac124f3def5d97b72fcf494a139e5f
Merged-In: I64c1210a8f04415b0b836db480463c172bcf0d71
(cherry picked from commit 24ffa6a5)