Add suffix .so to use directly libart.so

It should be the complete name with suffix .so to use libart.
At present, unnecessarily falls back like below.
"Falling back from libart to libart.so after dlopen error:
dlopen failed: library "libart" not found"

Change-Id: Ie5da35a71d6661434d2097c842407e6a254f8f58
Signed-off-by: randy.jeong <randy.jeong@samsung.com>
diff --git a/core/main.mk b/core/main.mk
index 7896d38..27b559f 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -333,7 +333,7 @@
 
 # Add build properties for ART. These define system properties used by installd
 # to pass flags to dex2oat.
-ADDITIONAL_BUILD_PROPERTIES += persist.sys.dalvik.vm.lib.2=libart
+ADDITIONAL_BUILD_PROPERTIES += persist.sys.dalvik.vm.lib.2=libart.so
 ADDITIONAL_BUILD_PROPERTIES += dalvik.vm.isa.$(TARGET_ARCH).variant=$(DEX2OAT_TARGET_CPU_VARIANT)
 ifneq ($(DEX2OAT_TARGET_INSTRUCTION_SET_FEATURES),)
   ADDITIONAL_BUILD_PROPERTIES += dalvik.vm.isa.$(TARGET_ARCH).features=$(DEX2OAT_TARGET_INSTRUCTION_SET_FEATURES)