g++ 4.8.2, shipped with Ubuntu 14.04, generates incorrect code for checking
the loop termination condition, resulting in never ending loops in
HashMapTest().
Disable the optimizations for this function for 4.8.[012] as the bug seems to
be fixed in 4.8.4 and several similar (but not really identical) bug reports
in gcc bugzilla have been fixed in 4.8.3.
This should allow the unit tests on Linux buildbots, using 4.8.2, to run to
completion again.
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