Don't append _asan to non-asan build flavors.

Right now we add the '_asan' suffix to the build flavor whenever
SANITIZE_TARGET is defined. This patch ensures the suffix is only
added when SANITIZE_TARGET=address.

Test: Checked flavor of SANITIZE_TARGET=address and integer_overflow
builds.
Bug: 30969751
Bug: 64561273

Change-Id: Ie20340f81b395e0b6b5f8086350bbc20f83d5fa4
diff --git a/core/Makefile b/core/Makefile
index fae81a4..ec2bf81 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -196,7 +196,7 @@
 # if it isn't already a part of the flavor (via a dedicated lunch
 # config for example).
 TARGET_BUILD_FLAVOR := $(TARGET_PRODUCT)-$(TARGET_BUILD_VARIANT)
-ifdef SANITIZE_TARGET
+ifneq (, $(filter address, $(SANITIZE_TARGET)))
 ifeq (,$(findstring _asan,$(TARGET_BUILD_FLAVOR)))
 TARGET_BUILD_FLAVOR := $(TARGET_BUILD_FLAVOR)_asan
 endif