Apply SANITIZE_TARGET and LOCAL_SANITIZE when both are present.

The idea is that targets with LOCAL_SANITIZE = signed-integer-overflow
and SANITIZE_TARGET=safe-stack should get both sanitizers.
This should work just fine for SANITIZE_TARGET=address, too.

Bug: 27729263
Change-Id: Ifee350da4877008fb061bc7f6c700e7fade405bc