updater_sample: add proguard.flags

Test: junit
Change-Id: I0175271935fdd87dd49ad9936d0e1b550d164e05
Signed-off-by: Zhomart Mukhamejanov <zhomart@google.com>
diff --git a/updater_sample/Android.mk b/updater_sample/Android.mk
index 7662111..a5deee1 100644
--- a/updater_sample/Android.mk
+++ b/updater_sample/Android.mk
@@ -20,9 +20,8 @@
 LOCAL_PACKAGE_NAME := SystemUpdaterSample
 LOCAL_MODULE_TAGS := samples
 LOCAL_SDK_VERSION := system_current
-
-# TODO: enable proguard and use proguard.flags file
-LOCAL_PROGUARD_ENABLED := disabled
+LOCAL_PRIVILEGED_MODULE := true
+LOCAL_PROGUARD_FLAG_FILES := proguard.flags
 
 LOCAL_SRC_FILES := $(call all-java-files-under, src)