sync_test: Use -fno-strict-aliasing

Use -fno-strict-aliasing here so we don't have to use it globally.
Performance on tests isn't important anyway.

Change-Id: I92ae7209ced60176cc5608f32b8ff6a911c09f10
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>