embunit: Use -fno-strict-aliasing

Use -fno-strict-aliasing to work around src/TestCaller.c line 54

Change-Id: Ic43e6f48527fb9a9e5b8baaadab132c638eba65e
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>