More flexibility to keep/remove R.class in static Java library

- Usually you don't need to set LOCAL_JAR_EXCLUDE_FILES in your
  Android.mk, if your static library is directly used by an app.
- If your library will be included by another library that need
  reference the R/Manifest class, you can set
  LOCAL_JAR_EXCLUDE_FILES := none
  to keep the generated classes.
- If your library includes another static library that has Android
  resource and you want to remove the generated classes carried by
  the static library, set:
  LOCAL_JAR_EXCLUDE_FILES := $(ANDROID_RESOURCE_GENERATED_CLASSES)

With the LOCAL_JAR_EXCLUDE_FILES value "none", deprecate the old
long variable LOCAL_KEEP_R_CLASS_IN_STATIC_JAVA_LIBRARY.

Change-Id: I3b9ad5d66f0262f784feb09bc1537c5b01256258
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index f3929ad..5209a04 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -122,9 +122,7 @@
 LOCAL_CTS_TEST_RUNNER:=
 LOCAL_CLANG:=
 LOCAL_ADDRESS_SANITIZER:=
-# Whether to keep the generated R/Manifest classes when building static Java library
-# with Android resource. false(default), or true
-LOCAL_KEEP_R_CLASS_IN_STATIC_JAVA_LIBRARY:=
+LOCAL_JAR_EXCLUDE_FILES:=
 
 # Trim MAKEFILE_LIST so that $(call my-dir) doesn't need to
 # iterate over thousands of entries every time.