_run never gets called any more, so the LD_LIBRARY_PATH wasn't being
set any more. The tests were still passing locally for me because the
tests were happily using the libc++.so from my system rather than the
one we build.
Wasn't obvious from the buildbot because the display for the test
results is absolutely terrible and they got lost in the noise of the
known failures.
Change-Id: Ib2df196ec6748718930e70887b7d0099884d792c
447998cbb0