Pass --legacy to aapt2 compile for Messaging

This module produces warnings that are treated as errors if --legacy
is not passed.  --legacy is no longer being passed by default, so
add it here.

Bug: 135617299
Test: m java
Change-Id: Ic001d8f4f9afdee3528929d3ba62a6bbade80ab6
diff --git a/Android.mk b/Android.mk
index 9309776..cad55d5 100644
--- a/Android.mk
+++ b/Android.mk
@@ -48,6 +48,7 @@
 
 LOCAL_AAPT_FLAGS += --version-name "$(version_name_package)"
 LOCAL_AAPT_FLAGS += --version-code $(version_code_package)
+LOCAL_AAPT_FLAGS += --legacy
 
 ifdef TARGET_BUILD_APPS
     LOCAL_JNI_SHARED_LIBRARIES := libframesequence libgiftranscode