build/core: Use better default compiler flags

Use -O3 for the compiler, -O2 for the linker

Change-Id: Ib9c3cd6d6ddf16c8bd20149a051ff2c17491a29d
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>

build/core: Don't use -fno-strict-aliasing

Don't use -fno-strict-aliasing: It's no longer needed.

Change-Id: I7b6e9524197dc152b57a8d1900dd6d7f9fe3452d
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>

build: Don't add -fno-strict-aliasing to HOST compiler flags

Change-Id: I07eef86f11ec3761e0922855cb6ff881c2773966
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>

build: Explicitly disable -Werror=strict-alising for HOST builds

Change-Id: Ib1e834951196ab3ea6acbe47c27eebe5633f55d2
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>