lttng-tools: resurrect -O1 workaround dropped by #21

This is needed currently, as our 2013.11 and 2014.05 IB 1 toolchains are
affected by gcc bug 58595, which is JIRA: CB-3083.

Signed-off-by: Christopher Larson <kergoth@gmail.com>
Merge pull request #22 from kergoth/resurrect-bug58595-workaround

lttng-tools: resurrect -O1 workaround dropped by #21