freetype: Build with -fno-strict-aliasing

Freetype's code is not quite ready to be built with strict
aliasing rules enforced.
Add -fno-strict-aliasing here so we can disable the global
-fno-strict-aliasing bit.

Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>
freetype: Don't force -O2

There's a -O2 hardcode in Android.mk - its purpose is to make
sure freetype gets built with optimizations enabled, but it
is done in a way that overrides other optimization flags such
as -O3 or -Os.

Only set -O2 if no other optimization level is requested.

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