Make asan more closely match clang behavior.

Always link libm with asan. Hasn't been a problem before because ASAN
was only ever used when libc++ was as well, which already links libm.

Pass --no-as-needed for host modules.

These aren't needed for the target builds because the target uses the
shared RTL.

Change-Id: I5d6a3c2dd557b5231be2b7711df6438693753a88

core/config_sanitizers.mk

@@ -78,7 +78,8 @@ ifneq ($(filter address,$(my_sanitize)),)
   ifdef LOCAL_IS_HOST_MODULE
     # -nodefaultlibs (provided with libc++) prevents the driver from linking
     # libraries needed with -fsanitize=address. http://b/18650275 (WAI)
-    my_ldlibs += -ldl -lpthread
+    my_ldlibs += -lm -ldl -lpthread
+    my_ldflags += --no-as-needed
   else
     # ASan runtime library must be the first in the link order.
     my_shared_libraries := $($(LOCAL_2ND_ARCH_VAR_PREFIX)ADDRESS_SANITIZER_RUNTIME_LIBRARY) \